Multiple sclerosis lesions in the brain and spinal cord can damage every function of the central nervous system. The clinical presentation varies from mild to aggressive symptoms and from relapsing-remitting to progressive disease, and the presentation changes in type of evolution over time. The protean symptoms include fatigue as well as disturbed function in sensory, motor, bladder, bowel, sexual, cerebellar, brainstem, optic nerve, and cognitive realms. Multiple sclerosis symptoms, especially fatigue, limit activity in three fourths of patients. The neuroanatomical location of plaques is not completely random. Lesions have a predilection for the periventricular white matter, so certain symptoms and signs are common. For instance, the medial longitudinal fasciculus has a periaqueductal location. Damage to the medial longitudinal fasciculus causes internuclear ophthalmoplegia, a frequent sign of multiple sclerosis.
In most patients, symptoms of an exacerbation arise over hours to days, typically last 2 to 6 weeks, and then remit, sometimes completely. Forty percent of these attacks cause long-lasting deficits (Lublin et al 2003; 2008), but 20% improve. Resolved symptoms can reappear transiently with infections or heat (“ghost symptoms,” Uhthoff phenomenon).
Fatigue from central lesions. Generalized physical and mental fatigue is the number one problem in two thirds of patients (Reder and Antel 1983; Noseworthy et al 2000). Patients describe fatigue as “profound”; it “disrupts life” and it is “different from any other experiences.” They say that because of the fatigue, “each day of the week at work is cumulatively harder,” and it gets “worse with heat.” The motor fatigue that normally follows muscular exertion is magnified (“fatigability,” in 75%) after sustained or repetitive muscle contractions and after walking; the fatigue often develops rapidly after minimal activity. It is distinct from weakness and may not correlate with weakness in individual muscles (Schwid et al 1999). Another type of fatigue is sometimes unprovoked (“lassitude,” “asthenia,” or “overwhelming tiredness,” in 20%). Fatigue limits prolonged neuropsychological testing. Rating scales of multiple sclerosis fatigue are difficult to design and correlate poorly with function because these symptoms are multidimensional. Self-reports often do not correlate with clinical measurements of muscle and cognitive fatigue.
Fatigue is an essential part of the neurologic history. Fatigue can be the only symptom of an exacerbation, or one of many. It is least common in primary progressive multiple sclerosis. Thirty percent of multiple sclerosis patients report fatigue before the diagnosis of multiple sclerosis (Berger personal communication 2011). Fatigue does not correlate with MRI plaque load, Gd enhancement, depression, or inflammatory markers. Fatigue, however, defined by the Sickness Impact Profile Sleep and Rest Scale (SIPSR), predicts later brain atrophy (Marrie et al 2005). It is associated with low prefrontal activity on PET, with reduced event-related potentials, and with low N-acetylaspartate in frontal lobes and basal ganglia on magnetic resonance spectroscopy.
Fatigue usually is worse in heat, in high humidity, and in the afternoon; body temperature is slightly higher in all these situations. This extreme sensitivity to heat is termed “Uhthoff phenomenon,” wherein a minimal elevation of body temperature interferes with impulse conduction by demyelinated axons because of their lower “safety factor.” Spasticity amplifies fatigue by creating resistance to movement, complicating routine actions. Central fatigue has been attributed to decreased Na+/K+ ATPase in multiple sclerosis plaques, disruption of the Kv 1.3 potassium channel in mitochondria, serum and spinal fluid neuroelectric blocking factors, neuronal dysfunction and exhaustion, axonal injury and poor axonal conduction, impaired glial function, poor perfusion of deep gray matter area, and the need to use wide areas of the cortex. Functional MRI for physical and cognitive tasks shows compensatory (inefficient) reorganization of the damaged CNS, with increased demand on remaining neurons. “Primary fatigue” is worst at midday.
In “non-primary fatigue,” contributors to fatigue and central conduction block are acidosis; lactate; heat after exercise; the rise in body temperature in the afternoon; and a half-degree centigrade rise in body temperature during the luteal phase post-ovulation; pain; poor sleep (daytime fatigue with waking at night, “middle insomnia,” often caused by need to urinate, and also spasms and itching and high incidence of sleep-related movement disorders); depression; low levels of dehydroepiandrosterone (DHEA) and its sulphated conjugate (DHEAS); inflammatory cytokines in the central nervous system [prostaglandins, tumor necrosis factor-alpha, and interferon-gamma (IFN-gamma)]. Insula lesions in stroke can cause underactivity and tiredness; the insular cortex atrophies in secondary progressive multiple sclerosis. Fatigue is associated with restless leg syndrome, circadian rhythm disruption, periodic limb movements, and hypersomnolence on sleep studies. A report of a specific brain sodium channel blocker (Brinkmeier et al 2000) could not be confirmed (Cummins et al 2003). Medications, hypothyroidism, anemia, and muscle deconditioning can contribute to fatigue.
Sleep disorders in multiple sclerosis are heterogeneous, often profound, and unexplained. Patients often complain of insomnia yet still have severe daytime fatigue. In small studies, CSF hypocretin (orexin) is normal in multiple sclerosis, unlike the low levels in narcolepsy. However, the frequent hypothalamic plaques in corticotrophin-releasing factor pathways could damage orexin-containing neurons. This would reduce input to the suprachiasmatic nucleus and disrupt circadian clock genes.
Autonomic problems. The hypothalamus controls autonomic functions, temperature, sleep, and sexual activity. Cortical, brainstem, and spinal cord lesions often interrupt the sympathetic nervous system. This causes slow colonic transit, bladder hyperreflexia, and sexual dysfunction. Other less-recognized phenomena from sympathetic nervous system disruption are vasomotor dysregulation (cold, purple feet), cardiovascular changes (orthostatic changes in blood pressure, poor variation of the EKG R-R interval on Valsalva maneuver, possibly increasing risk of surgery), poor pilocarpine-induced sweating, poor sympathetic skin responses—especially in progressive multiple sclerosis (Karaszewski et al 1990; Acevedo et al 2000), pupillary abnormalities, and possibly fatigue. Rarely, plaques in brainstem autonomic pathways cause atrial fibrillation or neurogenic pulmonary edema, sometimes preceded by lesion-induced cardiomyopathy. Sixty percent of patients have pupillary reactions that are abnormal in rate and degree of constriction (de Seze et al 2001). Pupillary defects do not correlate with visual-evoked potentials or history of optic neuritis. Autonomic dysfunction does correlate with axonal loss and spinal cord atrophy yet not with cord MRI lesions. It is possible that plaques in the insular cortex, hypothalamus, and cord all disrupt sympathetic pathways. Parasympathetic and sympathetic dysfunction correlates with duration of multiple sclerosis but not with disability (Gunal et al 2002). Parasympathetic dysfunction (eg, heart rate variation with respiration, abnormal pupillary reactions) is most pronounced in primary progressive disease. Sympathetic dysfunction (blood pressure response to straining) can worsen during exacerbations, and it is possibly tied to dysregulated immunity (Flachenecker et al 2001), less response to the beta-adrenergic agonist, isoproterenol (Giorelli et al 2004), and conversion to progressive multiple sclerosis.
Periodic hyperthermia and profound hypothermia (to 28C/79F, author’s observation) are occasionally seen. Cognition is surprisingly preserved with hypothermia. These patients are at high risk for infection because immunity is compromised at low temperature. Conversely, worsening hypothermia can forecast an infection. Abnormal temperature regulation is presumably from hypothalamic or thalamic plaques.
Cognitive function. Higher cortical functions, language skills, and intellectual function usually appear normal to a casual observer. However, careful clinical observation and sensitive neuropsychological tests find slight to moderate cognitive slowing, slow information processing, word-finding difficulties, poor recent “explicit” memory, poor clock-drawing, and decline in effortful measures of attention in 50% of patients (Rao et al 1991; Beatty 1999; Arnason 2005). Up to half of patients with clinically isolated syndromes are significantly impaired on some tests. Complaints range from “I always forget where I put my keys” and “the lights are off in the factory” to “I am no longer able to perform cube roots in my head.” These subcortical signs often appear during complex tasks (especially with use of affected limbs), with speeded responses, during working memory, and when multiple visual and sensory stimuli confront the patient: “I feel like I live in an IMAX theater.” The simple question, “Do you have trouble walking through a shopping mall?" is often met with an anguished, "Yes, it’s too overwhelming.”
Patients should be screened for cognitive problems at the first exam. Patients with normal cognition tend to maintain cognitive levels, but mild cognitive deterioration predicts progressive decline in cognition over 3 years. The best measure of cognitive slowing (information processing speed, sustained and complex attention, and working memory) appears to be the symbol digit modalities test (SDMT). Mood swings, irritability, and frustration from slow cognition are common. The family may notice impairment before the patient does. When disputed by the family, complaints of cognitive decline suggest depression. Cognitive deficits are most pronounced in secondary progressive disease, but often do not correlate with physical disability. Cognitive decline leads to difficulty with employment and daily life. Patients have more difficulty walking while performing cognitive tasks. Neuropsychological evaluation can review residual strengths and weaknesses for employment, social function, and driving ability; evaluation can also investigate depression and lead to therapy.
Decision making is compromised from slower learning plus impaired emotional reactivity. Occasionally, patients go through a phase of wildly illogical thinking that later resolves as the disease progresses. “Low anxiety” leads to inconsistent, risky decisions in a Gambling Task and predominates in early multiple sclerosis (Kleeberg et al 2004). Impulsivity correlates with loss of anterior corpus callosum integrity in cocaine-dependent subjects and possibly also in multiple sclerosis.
Some patients have nearly normal neurologic exams yet are unable to walk from poor patterning of leg movement and gait. Electrophysiological tests confirm this apraxia and show impaired input to the motor cortex and to pathways involved in motor planning. Spinal learning may also be impaired (Arnason 2005).
Patients with mild cognitive impairment have cortical thinning on MRI. Chronic cases have extensive hippocampal demyelination (Geurts et al 2007), although cognition is less affected in primary progressive multiple sclerosis. T1 brain and corpus callosum atrophy, third ventricular width, and T2 lesion load correlate modestly with poor cognition. Basal ganglia hypointensity and atrophy (brain parenchymal fraction) correlate modestly with decreased memory. Retinal nerve fiber layer thickness, however, correlates quite well with symbol digit modality tests (r=0.754) (Toledo et al 2008). Global N-acetyl aspartate has a moderate correlation with cognitive loss. Decreased attention correlates with lower N-acetylaspartate in the locus ceruleus in relapsing-remitting patients.
On functional MRI, decreased activation of the cerebellum correlates with poor motor learning. Excessive activation (poorly focused) in the supramarginal gyrus, insula, and anterior cingulum correlates with poor episodic memory (Rao personal communication 2005). Excess activation also links to less hand dexterity, suggesting greater allocation of cognitive resources. Conventional MRI and functional MRI (fMRI) abnormalities correlate with slow psychomotor speed and increased risk of driving accidents. Positron emission tomography (PET) shows cortical hypometabolism above subcortical plaques. Cognitive impairment in rats with experimental allergic encephalomyelitis lasts long after inflammatory lesions have resolved.
Low bone density is associated with cognitive impairment (Weinstock-Guttman personal communication 2011). This may be a consequence of loss in CNS input to bone or to an underlying cytokine abnormality.
Exacerbations can reduce cognition, sometimes as the sole symptom. B Arnason argues that memory problems appear during exacerbations in early multiple sclerosis, coincident with T cell inflammation in the CNS. Later in the disease, cognition is increasingly impaired, coincident with greater monocyte and microglial activation and monokine secretion (Arnason 2005).
Visual memory declines in multiple sclerosis. Visual pathways course from optic nerves, around the ventricles to the occipital cortex, and back around the ventricles to temporal memory areas. Visual pathways are likely to be interrupted by periventricular plaques and inflammatory cytokines. IFN-beta therapy benefits visual memory (below).
Aphasia is rare in multiple sclerosis but can arise in acute disseminated encephalomyelitis.
Depression. This topic is extensively reviewed by Arnason (Arnason 2005). The incidence of depression is increased 2- to 3-fold in multiple sclerosis patients (>50%) and their families. Severe, short-duration multiple sclerosis is associated with more depression, but primary progression is associated with less depression. Plaques and hypometabolism in the left arcuate fasciculus (supra-insular white matter) (Pujol et al 1997), right temporal (Berg et al 2000), and left temporal and inferior prefrontal areas (Feinstein et al 2004) are associated with depression. However, depression does not correlate with MRI burden of disease or atrophy, disability, or cognitive deficits.
The dexamethasone suppression test is a marker of neuroendocrine function in depression. It is abnormal during active multiple sclerosis (Reder et al 1987; Fassbender et al 1998), possibly from chronic inflammation, cytokine stress, and induction of CRH/AVP in hypothalamic neurons. During attacks, depression and cytokine levels are strongly correlated [tumor necrosis factor-alpha, IFN-gamma, and interleukin 10 (IL-10) all rise] (Kahl et al 2002), possibly because IFN-gamma increases serotonin transporter and indoleamine dioxygenase levels, lowering serotonin.
Therapy with IFN-beta can occasionally trigger depression, probably because interferon elevates indolamine-2,3-dioxygenase, which lowers levels of tryptophan and serotonin. However, IFN-beta therapy as well as antidepressants could elevate brain serotonin by decreasing IFN-gamma levels. Both agents induce brain-derived neurotrophic factor. Surprisingly, patients taking anti-depressants have lower BDNF levels in circulating immune cells (Hamamcioglu and Reder 2007), possibly because depressed multiple sclerosis patients have low BDNF levels before antidepressant therapy.
Suicide is elevated 7-fold in multiple sclerosis. Suicidal patients are more likely to have a family history of mental illness, to abuse alcohol, to be under social stress or be depressed, and to live alone. Confused thoughts and occasionally psychosis can be seen with exacerbations.
Pseudobulbar affect (pathological laughing and crying, involuntary emotional expression disorder) can be disabling. Disinhibition is from multiple supratentorial plaques and is occasionally associated with hiccups and paroxysmal dystonia. Euphoria, despite concurrent neurologic problems, was described by Charcot. It is possible the euphoria is cytokine-mediated, akin to “spes phthisica”—a feeling of hopefulness for recovery seen in patients with tuberculosis.
Optic neuritis. The optic nerves are frequently involved (approximately 2/3 clinically), especially in younger patients. Thirty-one percent of army recruits with multiple sclerosis have optic signs. “Asymptomatic” patients, free of optic neuritis, frequently have abnormal visual evoked potentials or perimetry.
Optic neuritis typically begins with subacute loss of vision in 1 eye. The central scotoma is described as blurring or a dark patch. Color perception and contrast sensitivity are also disturbed. Subjective reduction of light intensity is often associated with an ipsilateral Marcus Gunn hypoactive pupillary response. Ninety-two percent have retro-orbital pain with eye movement.
With acute lesions, there may be blurring of the disc margin or florid papillitis. With papillitis (in 5%), inflammation near the nerve head can cause disc-swelling, cells in the vitreous, and deep retinal exudates. When the inflammation is retrobulbar, the fundus is initially normal. After the neuritis resolves, the disc is usually pale ("optic pallor"), commonly in its temporal aspect. Slit-like defects in the peripapillary nerve fiber layer can be seen with red-free (green) light using an ophthalmoscope. This axonal damage in the retina, an area free of central nervous system myelin, suggests that optic nerve pathology extends beyond central nervous system plaques. Retinal nerve fiber layer atrophy and thinning is obvious on optical coherence tomography (OCT). On OCT, the fellow eye is often abnormal, though not as severe.
Bilateral simultaneous optic neuritis led to multiple sclerosis in 1 of 11 adults after an interval of up to 30 years. Sequential optic neuritis led to multiple sclerosis in 8 of 20 (Parkin et al 1984). In children, 1 of 17 developed multiple sclerosis after bilateral onset.
Visual function usually begins to improve several weeks after the onset of optic neuritis, and resolution continues over several months. Complete recovery of visual acuity is the rule, even after near blindness. Other disturbances of vision, however, often persist, such as visual "blurring" and red or blue desaturation that causes colors to appear drab (“not as vivid”). There is progressive loss of color discrimination with longer duration multiple sclerosis. Bright lights cause a prolonged afterimage, a "flight of colors." Depth perception is impaired and is worse with moving objects (“Pulfrich phenomenon”). Eye movements sometimes cause fleeting flashes of light (“movement phosphenes”). The mechanism corresponds to the fleeting cervical sensory changes of Lhermitte sign (Lhermitte of the eye). Increased body temperature can amplify all of these symptoms and diminish visual acuity (“Uhthoff phenomenon”).
Uveitis and pars planitis (peripheral uveitis) are present in 1% of multiple sclerosis patients. Conversely, 20% of patients with pars planitis develop multiple sclerosis or optic neuritis. Some of these patients will develop macular edema, vitreous opacities, papillitis, vasculitis and vitreous hemorrhage, and cataracts. Perivenous sheathing is an inflammatory change of the retina seen in one fourth of multiple sclerosis patients. Cortical lesions can distort vision, eg, visual inversion.
Brainstem abnormalities, including diplopia. Lesions in the brainstem disrupt intra-axial nerves, nerve nuclei, internuclear connections, plus autonomic, motor, and sensory long tracts. Sixth or third nerve and rarely fourth nerve lesions cause diplopia. Cerebellar and brainstem lesions cause eye movement abnormalities, usually coinciding with more severe disability. Proton density MRI is the best way to image abnormalities in the brainstem, including plaques in the median longitudinal fasciculus. There are reports of high T2 signal MRI lesions in peripheral third, fifth (in 2% of patients, with two thirds bilateral), and eighth nerves.
Medial rectus weakness is usually part of an “internuclear ophthalmoplegia” (INO). In a young patient, INO is nearly pathognomonic of multiple sclerosis. Infarcts, trauma, and disparate other causes are possible, especially in older patients (Keane 2005). Internuclear ophthalmoplegia is paresis or weakness of adduction ipsilateral to a medial longitudinal fasciculus lesion, along with dissociated nystagmus of the abducting eye. Lesions, usually in the pons or midbrain, cause internuclear ophthalmoplegia when they interrupt connections between the pontine paramedian reticular formation that innervates the ipsilateral abducens nucleus and the contralateral third nerve nucleus. This illustrates an important principle: plaques predominate in periventricular regions and cause characteristic signs.
Internuclear ophthalmoplegia is subclinical or “latent” in 80% of patients (in this case, it would be termed “internuclear ophthalmoparesis”). Rapid eye movements can bring out this hidden, minimal oculomotor weakness, causing slowing of the early adducting saccades—an adduction lag. A medium rate of finger motion will detect loss of smooth pursuit and demonstrate ataxic eye movements from cerebellar lesions. Convergence may be normal despite an affected medial rectus. Medial longitudinal fasciculus lesions are seen best with proton density MRI but are even more apparent with the clinical exam. Internuclear ophthalmoplegia is often worse with heat and better with cooling (Frohman et al 2008).
Nystagmus is common in multiple sclerosis. It is usually inconsequential, but nystagmus and oscillopsia can be severe enough to prevent reading or driving a car.
Seventh nerve lesions mimic Bell palsy. Because the lesions are intra-axial, the sixth nerve is often simultaneously disturbed. Facial myokymia is from pontine tegmentum lesions of the facial nerve and can be revered with carbamazepine and possibly botulinum toxin.
Hearing loss is relatively rare, but auditory processing could be slowed by brainstem and deep white matter lesions. Central hearing defects could be supported by brainstem auditory evoked potentials. They could also differentiate multiple sclerosis from benign positional vertigo, which has no central defect. Vertigo is common and sometimes so incapacitating that patients are bed-bound. Isolated autoimmune disease of the auditory nerve can also cause hearing loss and vertigo. The relation to multiple sclerosis is unclear.
Up to one fourth of patients have problems swallowing. Horner syndrome is occasionally present.
Transverse myelitis. The cord symptoms in idiopathic transverse myelitis are generally more severe than in multiple sclerosis. In multiple sclerosis, a complete transverse lesion is less common than a partial cord lesion (ie, a Brown-Séquard syndrome).
Cerebellar dysfunction and tremor. The cerebellum or its pathways are damaged in 50% of patients. "Charcot’s triad" of cerebellar signs is nystagmus, intention tremor, and “scanning” speech (in the sense of examining words carefully, “scandés” from Charcot). In 3% of patients, intention tremor of the limbs, ataxia, head or trunk titubation, and dysarthria can be totally disabling. Dentate lesions correlate with poor ambulation. Surprisingly, patients with severe ataxia are often strong and thin and would otherwise be fully functional. The Stewart-Holmes rebound maneuver to detect cerebellar dyssynergia does not correlate well with kinetic tremor (flex or extend at elbow) and intention tremor (finger-to-nose). This suggests damage to different anatomic pathways (Waubant et al 2003). Poor cerebellar function correlates with loss of cerebellar volume on MRI.
Dystonia and parkinsonian symptoms are occasionally caused by a multiple sclerosis plaque. Severe cerebellar signs correlate with poor pulmonary function.
Weakness. The long course of axons traveling from the motor cortex through the cord to the lumbar motor neurons increases the likelihood that a random plaque will interrupt motor neuron conduction. Legs are usually affected more than arms. Patients complain of a foot-drop, tripping, or poor stair climbing. The hip flexors are often weak and out of proportion to other leg muscles, likely from multiple cervical cord lesions (D Garwacki). Patients can walk backwards more easily than they walk forward because gluteal muscles are stronger than the iliopsoas. Hyperreflexia, spasticity, and a Babinski sign are common. Rarely, plaques interrupt intra-axial nerve roots, and the deep tendon reflexes disappear and muscles atrophy. Radicular symptoms arising from a posterior cord lesion are often painful, but anterior plaques are not. Some muscle weakness and fatigue can be explained by a shift in myosin heavy chain isoforms and less contractile force, a result of muscle inactivity and deconditioning (Garner and Widrick 2003). Walking ability can be measured with a timed 25-foot walk or the 6 spot step test, which incorporates coordination and balance.
Spasticity. Spasticity increases with a full bladder or bowels, pain, exposure to cold, and sometimes on the day after IFN-beta injections (an effect of cytokines or direct modification of neuronal excitability). There is often transient stiffness after physical inactivity. On arising, the first few steps are difficult. Similarly, internuclear ophthalmoplegia is most obvious with the first eye movements of the exam. Painful tonic spasms are common in patients with severe spasticity and are sometimes provoked by exertion or hyperventilation. Extrapyramidal symptoms disappear when the causative plaque resolves (Maimone et al 1991b).
Bladder and sexual dysfunction. Bladder dysfunction is common and markedly reduces quality of life. It is the initial symptom in 5% of patients and eventually develops in 90%. Two thirds of patients have bladder hyperreflexia with urgency and frequency. This is complicated by sphincter dyssynergia in half of the patients (Schoenberg 1983; Andrews and Husmann 1997; Betts 1999). Some of these patients are initially areflexic. The other third of symptomatic patients have hyporeflexic bladders. Patients’ description of residual volume is often unreliable, so volume should be measured with office sonography or catheterization. Detrusor hyporeflexia is linked to pontine lesions; detrusor-sphincter dyssynergia is linked to cervical spinal cord lesions. Both are more common in Japanese populations than in Western populations.
Glomerular filtration rate is reduced by 20% (Calabresi et al 2002). This could be from chronic neurogenic bladder, urinary tract infections, antibiotics, ionic contrast agents, non-steroidal anti-inflammatory drug use, and chronic dehydration.
Seventy percent of patients complain of sexual problems—orgasmic difficulty, poor erections or lubrication, low pleasure, low libido, poor movement, and genital numbness. Impotence develops in 40% to 70% of male patients. Fifty percent of women with multiple sclerosis have significant sexual problems and complain of loss of libido, orgasms, and genital sensation. Orgasmic dysfunction correlates with loss of clitoral vibratory sensation and cerebellar deficits (Gruenwald et al 2007). Difficult or no orgasm was associated with abnormal or absent (26/28) pudendal somatosensory evoked potential, although desire was normal (Yang et al 2000). Occasionally, women have diffusely felt orgasmic spasms, not in skeletal muscle, that last for up to 5 minutes. Others mention increased vaginal sensation and orgasmic intensity.
Sexual problems often follow or coincide with bladder dysfunction. They are often associated with loss of sweating below the waist from lesions of the sympathetic pathway and also with disruption of genital somatosensory pathways. MRI T1 lesions in the pons correlate with sexual dysfunction, far better than other MRI measures, urodynamics, or pudendal and tibial evoked potentials. Other literature varies on anatomical links to plaque location.
Constipation. Constipation is experienced by 50% of clinic patients and is more prevalent in progressive than in relapsing forms. Poor voluntary squeeze pressure on manometric testing, combined with little sensation of “fullness” is typical. Insensitivity to rectal filling causes incontinence. This is uncommon but not rare and is usually associated with constipation. Disruption of autonomic pathways in the cord may underlie the constipation. Gut neurons have not been studied as direct targets of the immune system in multiple sclerosis, but enteric glia have more antigenic resemblance to glia in the central nervous system than glia in the peripheral nervous system (Gershon et al 1994).
Sensory symptoms. Sensory symptoms are common. Sensations are characteristically hard to describe because they are spontaneous or distorted perceptions of everyday stimuli caused by areas of demyelination and ephaptic connections unique to each patient. Sensory loss ranges from decreased olfaction to marked loss of pain perception in small spots or over the entire body. Poor perception of vibration in the feet, but spared position sense, is present in more than 90% of multiple sclerosis patients. Vibratory loss can be quantified with a tuning fork and sometimes improves with drug therapy. Sensory paths are unable to transmit impulses from the rapidly oscillating tuning fork, a combination of demyelination and cytokines that interfere with axonal conduction (Smith et al 2001). Positive sensory symptoms are also common. Tingling, numbness, a tight band (usually at T6-T10, the “multiple sclerosis hug”), pins and needles, a dead feeling, “ice” inside the leg, standing on broken glass, and something "not right" are common descriptions. Paresthesias typically begin in a band (a “multiple sclerosis hug”) around the trunk at T6-T9 (often from a cervical plaque). They sometimes start in a hand or foot and progress over several days to involve the entire limb. The sensations then resolve over several weeks.
Lhermitte sign. In 1924, Lhermitte described an electric discharge following flexion of the neck in multiple sclerosis. Forty percent of multiple sclerosis patients have Lhermitte sign (symptom, phenomenon). This is rapid, brief "electric shock" or "vibration" running from the neck down the spine, similar to when trauma to the ulnar nerve triggers the “funny bone.” The intensity of the pain is directly related to the amplitude and rapidity of neck flexion. In an instinctive protective reflex, the patient may straighten her neck. This sign is from mechanical stimulation of irritable demyelinated axons. Ninety-five percent of patients with this sign have cervical cord MRI lesions. Cord compression can also generate the sign and must be ruled out.
Pain. Up to two thirds of patients with multiple sclerosis have pain at some time during the course of their disease (Clifford and Trotter 1984; Moulin et al 1988; Stenager et al 1991), although pain was regarded as rare in much of the older literature. The pain is chronic most of the time, but acute or intermittent pain also occurs. Legs are affected in 90%, and arms in 31%, of patients complaining of pain. Pain is more common in older women with spasticity or myelopathy, and in multiple sclerosis of long duration (Moulin et al 1988; Stenager et al 1991). It is often worse at night and when the ambient temperature changes suddenly.
The spectrum of pain includes central neuropathic pain from focal demyelination (eg, trigeminal neuralgia, dysesthesias, and nonspecific pain) to pain and dysesthesias from ephaptic transmission (Lhermitte symptom, radicular pain, tonic seizures), inflammation or swelling (optic neuritis, headaches), visceral pain from chronic constipation or painful bladder spasms, abnormal motor activity (tonic seizures, spasms, clonus), or simple orthopedic musculoskeletal pain. Lesions in pain inhibitory pathways, abnormal sodium channel redistribution, or maladaptive neural plasticity during plaque repair may cause the central pain. Chronic back pain can arise as a consequence of multiple sclerosis, causing unilateral weakness or spasticity, poor posture, and accelerated degenerative disc disease.
Pain is common in optic neuritis. A swollen, inflamed optic nerve puts pressure on the dural sheath. Pain in or behind the eye sometimes precedes the visual loss. The pain in optic neuritis can be present at rest, on voluntary eye movement, and with pressure on the globe. Vasoactive amines, prostaglandins, and kinins released by inflammatory cells may magnify the pain in optic neuritis and in trigeminal neuralgia.
Trigeminal neuralgia. Trigeminal neuralgia is relatively rare in multiple sclerosis (occurring in 0.5% to 1% of patients) (Rushton and Olafson 1965). Bilateral trigeminal neuralgia has been described as pathognomonic of multiple sclerosis (Jensen et al 1982). However, it can be caused by vascular lesions (Meaney et al 1995) when arteries compress the trigeminal nerve at the junction of the central and peripheral nervous system (root entry zone). Vascular compression causes demyelination and remyelination, sometimes aberrant, allowing ephaptic conduction between active and silent nerve fibers, and between light touch and pain fibers (Love and Coakham 2001).
The trigeminal neuralgia of multiple sclerosis is from a plaque in the fifth nerve nucleus (Olafson et al 1966) or the brainstem entry zone of nerve fibers (Gass et al 1997). After facial nerve injury, IFN-gamma increases, but pituitary adenylyl cyclase-activating polypeptide recruits anti-inflammatory Th2 cells. Radicular pains in multiple sclerosis, especially if lancinating, may have a similar mechanism. The cisternal (peripheral) fifth nerve enhances on MRI in 3% of patients, but this is usually clinically silent.
Brainstem plaques can cause glossopharyngeal neuralgia.
Headaches. Headaches are more common in multiple sclerosis (27%) than in matched controls (12%) (Watkins and Espir 1969). They can herald exacerbations.
Seizures and paroxysmal symptoms. Epileptic seizures double in incidence in multiple sclerosis and are more common in later stages. They seem to result from new or enhancing lesions in the cortex or subcortical areas. They can be triggered by 4-amino pyridine or rapid reductions in baclofen.
Other paroxysmal symptoms last seconds to minutes and are triggered by hyperventilation (eg, 20 deep breaths), stress, cold, touch, metabolic abnormalities, exercise, or acute exacerbations. Paroxysms include visual complaints, diplopia, vertigo, dysarthria, facial and limb myokymia, tonic motor seizures, spasms, dystonia, restless legs, akinesia, kinesigenic choreoathetosis, hyperekplexia, rapid eye movement sleep disorders, ataxia, itching, and pain and paresthesias (eg, trigeminal neuralgia, Lhermitte sign). Transverse spread between demyelinated axons (ephaptic transmission) is a likely cause. It is probably amplified by cytokines, extracellular potassium, dysfunction of ion channels, and heterogeneity of new sodium channels.
Associated diseases. In multiple sclerosis, there are links between inflammatory bowel disease and thyroiditis, and bone mass is low. Other autoimmune diseases are not associated with multiple sclerosis—and may be less prevalent than in the general population. Many reported associations are likely from the strong autoimmune proclivity in Devic disease or CNS Sjögren disease, variants that comprise 5% of “multiple sclerosis” patients. Cancer incidence is likely reduced.
Natural history. The course of multiple sclerosis varies. Heterogeneity over time complicates the use of stage-specific therapies. Classification is important because no therapies are effective in the primary progressive forms.
At onset, at an average of 28 years old, multiple sclerosis is relapsing-remitting 85% of the time. This form predominates in young women. Attacks typically occur once every 2 years. Survival is decreased by 10 years.
Fifty percent of relapsing-remitting patients become progressive after 10 years, and 89% by 26 years; this is termed "secondary progressive” multiple sclerosis. The number of neurologic systems in the initial attack, and not recovery from the attacks, predicts the chance of developing progressive disease. Once progression appears, the rate of decline is constant.
About 10% to 15% are progressive from onset, at an average of 38 years old, with continuing deterioration for a year or more, without obvious exacerbations or remissions, although the rate of decline fluctuates. Compared to age 10 to 19 years, the relative risk of primary progression is 2.3 at age 25, 8.1 at 35, 19 at 45, and 47-fold higher at age 50 to 59 years (Stankoff et al 2007). These categories are not immutable; patients frequently drift from one type of multiple sclerosis to another, become stable, or suddenly develop active disease (Goodkin et al 1989). Primary progression is considered a unique form of multiple sclerosis, but 28% of these patients will eventually have exacerbations (Kremenchutzky et al 1999), sometimes after 20 years of pure progression.
The progressive form affects the spinal cord predominantly (in 90%), begins at a later age (40 years) than the relapsing form, and is approximately as common in men as in women. These patients have progressive paraparesis and loss of vibration and pinprick sensation in the legs, and they typically develop a small, spastic neurogenic bladder. Cerebral MRI lesions are 6 times less frequent in the primary progressive group compared to relapsing-remitting patients who become progressive later on (Thompson et al 1991). However, in white matter that appears normal on conventional MRI, low N-acetyl aspartate levels are low (reflecting widespread neuronal loss or dysfunction), and the magnetization transfer ratio is low (Filippi et al 1999). Relapses in the first 2 years predict earlier onset of progression. Relapses after the first 2 years are linked to lower chance of becoming progressive (Scalfari et al 2010), suggesting that evolution of immune dysregulation modifies the course of multiple sclerosis. Progression has features of an age-dependent degenerative process (Kremenchutzky et al 2006). Age at onset of multiple sclerosis is 30 years for secondary progressive disease but 39 years for primary progressive multiple sclerosis. Age at beginning of progression is 39 in both groups.
Exacerbations contribute to disability. Forty-two percent to 49% have residual loss of 0.5 EDSS points at 2 to 4 months, and 28% to 33% have a loss of 1 or more EDSS point (Lublin et al 2003; Hirst et al 2008). Some improve; however, 19% have a 0.5 point decrease and 10% have a 1 point decrease (Lublin et al 2003). In 700 placebo-treated patients from 11 clinical trials, worsening after exacerbations was nearly equivalent to improvement (Ebers et al 2008). The authors conclude that disability could not be used as an outcome measure in most (short-term) clinical trials.
Occasionally, patients have acute fulminant multiple sclerosis (Marburg variant). This malignant form of multiple sclerosis is possibly associated with developmentally immature myelin basic protein (Wood et al 1996).
Twenty percent of patients have “benign multiple sclerosis,” defined as a Kurtzke disability score of 3/10 or lower. After 20 years, 6% of the overall population is still benign—largely comprised of those who scored 2 or lower at 10 years (Hawkins and McDonnell 1999). Some patients with benign multiple sclerosis have surprisingly large lesion loads on MRI (Strasser-Fuchs et al 2008). Clinical/MRI dissociation is also seen in correlating MRI with clinical activity (r is only 0.25). Predictors include young onset, monosymptomatic, no cord symptoms, and few attacks or MRI lesions. Cognitive function, fatigue, and pain should be included in assessment of a propitious course. Autopsy studies indicate that there is a large reservoir of undetected and, therefore, benign multiple sclerosis.
Unsuspected and asymptomatic cases. Multiple sclerosis is sometimes unsuspected during life, yet found at autopsy. Twelve unsuspected cases of multiple sclerosis were found in 15,644 autopsies in Switzerland. Only 2 had no reported neurologic signs during life (Georgi 1961). There were 5 diagnosed cases of multiple sclerosis in 2450 autopsies in London and Ontario (Gilbert and Sadler 1983). In autopsy studies, the calculated prevalence of unsuspected multiple sclerosis would be about 31 in 100,000 in Paris (3 in 9300) (Castaigne et al 1981); 90 to 128 in 100,000 in Switzerland (Georgi 1961); and 204 in 100,000 in Ontario (Gilbert and Sadler 1983). This suggests that the number of undiagnosed "normal" people with multiple sclerosis approximates the number of patients diagnosed with multiple sclerosis. Of asymptomatic “normal” first degree relatives, 4% to 10% have MRI lesions indistinguishable from multiple sclerosis (De Stefano et al 2006). This suggests that “benign” multiple sclerosis is itself a spectrum, and sometimes should not be treated with immunomodulators.
Clinically isolated syndromes. “Clinically isolated syndromes” include optic neuritis, transverse myelitis, and solitary brainstem lesions. They evolve into multiple sclerosis most often when the MRI T2 lesion load is high and when the CSF reflects inflammation. When clinically isolated symptoms appear in parallel with non-enhancing MRI lesions plus at least 1 enhancing lesion, 70% to 80% of patients will have another gadolinium-positive lesion within 6 months. A positive spinal tap further increases the chance that multiple sclerosis will develop. Partial cervical myelopathy, without brain MRI lesions, often evolves into clinically definite multiple sclerosis if evoked potentials and CSF are abnormal (Bashir and Whitaker 2000).
Childhood multiple sclerosis. An attack before the age of 16 happens in 3% to 5% of all patients. A family history (8%) is more common than in adult forms. Sensory symptoms and optic neuritis are common (approximately 50%, even though these symptoms may sometimes not be reported by children). Brainstem and cerebellar symptoms, polysymptomatic disease, and seizures are more frequent than in adult onset multiple sclerosis, but recovery from exacerbations is better (Duquette et al 1987; Selcen et al 1996; Ghezzi et al 1999; Ruggieri et al 1999). One third of patients have cognitive problems. As in adult forms, sphincter involvement and a progressive course have a poor prognosis. Boys predominate over girls between 8 and 10 years of age, but the girl-to-boy ratio is 2:1 after 10 years. Relapses are a bit more frequent in childhood (every 1.6 years versus every 2 years in adults) but are only 4 weeks long versus 7 weeks in adults (Ness et al 2007). The course is slower than in adult-onset multiple sclerosis (Simone et al 2002), and the median time from onset to secondary progression is 28 years. Nonetheless, with continuous exacerbations they become disabled at a younger age than adult-onset patients. Primary progression is exceptionally rare (2% of an already uncommon event).
MRI, EEG, and visual-evoked potentials are each abnormal in 80% of patients, and CSF is abnormal in 66% of patients (CSF IgG levels are lower in children, so this is probably an underestimate) (Duquette et al 1987; Banwell 2004). Oligoclonal bands are uncommon in acute disseminated encephalomyelitis, a disorder sometimes difficult to separate from the first attack of multiple sclerosis. Bands are positive in 29% of acute disseminated encephalomyelitis, 64% of acute multiple sclerosis, and 82% of multiple sclerosis at later times in a medium-sized series (Dale et al 2000). Serum antibodies to myelin oligodendrocyte glycoprotein are increased in frequency in children versus adults. The prolonged relapsing-remitting course suggests therapies may be more effective in children than in adults. [Neurology 2007;68(16, Suppl 2) is devoted to pediatric multiple sclerosis.]
Geographic variation. The incidence and symptoms of multiple sclerosis are different around the globe. It is uncommon at the equator (prevalence 2 to 10 per 100,000), and increases with distance from the equator (up to 200 per 100,000). This suggests environmental factors influence the incidence, but emigrating northern Europeans tended to stay in temperate climates, suggesting genetic influence. Multiple sclerosis is rare in Asia (4 per 100,000) (Kurtzke 1975). Multiple sclerosis in Japan, China, Malaysia, in black Africans, and in some groups of Canadian Aboriginals often resembles Devic disease because it typically affects the optic nerves and spinal cord and occurs at an earlier age than the Western form of multiple sclerosis (Cosnett 1981; Phadke 1990).
Quality of Life (QOL) and clinical scales. Responses by 433 patients were used to generate the 59-question Functional Assessment of Multiple Sclerosis quality of life scale (Cella et al 1996). A factor analysis demonstrated that multiple sclerosis had independent effects on several important factors that impact patients’ lives.
Separate axes with little overlap included the following:
Neurologic and social function, fatigue, mood, and cognition are important components of clinical multiple sclerosis that are often more disabling than inability to walk. Because these factors do not correlate, different pathogenic mechanisms are likely. For example, difficulty walking could arise from damage to long tracts or oligodendroglia, and fatigue may be caused by inflammatory cytokines in the CNS. Different pathological causes may also vary in responses to drugs; they should all be evaluated in therapeutic trials.
Patient-rated scales provide important information about independent factors that are missed when exams are limited to assessment of mobility. Telephone and self-administered scales correlate well (r=0.9) with physician exams.
The Kurtzke Extended Disability Status Score (EDSS) is a central clinical measure in most trials. It is based on the neurologic exam and ranges from 0 to 10, where 0 = normal, 4 = walks unaided for greater than 500 meters, 5 = walks unaided for greater than 100 meters, 6 = needs a cane to walk 100 meters, 7 = walks less than 20 meters with aid, 8 = perambulated in wheelchair, and 10 = death. Cognitive problems, fatigue, sexual function, job capabilities, and social factors do not weigh heavily in this scale. This scale is not linear, and transition between stages 4 and 6 is fastest.
The Multiple Sclerosis Functional Composite Scale (MSFC) evaluates motor function of legs and arms and cognition. It adds information to the Kurtzke Expanded Disability Status Score and was used in a phase 3 clinical trial of intramuscular IFN-beta-1a (Cohen et al 2001). Correlation between the Kurtzke scale and the Multiple Sclerosis Functional Composite scale is only r = -0.15.
The global Multiple Sclerosis Severity Scale (MSSS) combines disease duration with the Kurtzke score to combine rate and severity (Roxburgh et al 2005). Many of the patients who defined the MSSS were on therapy, so untreated progression rates are probably even higher than the table indicates.