Hyperventilation syndrome is one of the most common causes of dizziness and paresthesias presenting to neurologists, and yet, it is underdiagnosed. Interestingly, hyperventilation not infrequently produces predominantly unilateral paresthesias that are more often on the left side, which can be confused with partial seizures, cerebrovascular disease, and multiple sclerosis. Patients may report a variety of psychological complaints, including anxiety, nervousness, unreality, disorientation, or feeling "spacy." Impairment of concentration and memory may be described as part of episodes. Déjà vu or auditory and visual hallucinations can rarely occur.