Morvan syndrome and related disorders associated with CASPR2 antibodies
Jan. 18, 2022
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Hyperventilation syndrome is one of the most common causes of dizziness and paresthesias presenting to neurologists, and yet, it is underdiagnosed (73). 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.
• Neurologists frequently see patients with hyperventilation syndrome with dizziness and bilateral paresthesias.
• Ninety-nine percent of cases are chronic hyperventilation syndrome (modest increase in respiratory rate or tidal volume).
• The paresthesias may be unilateral in 16% of patients, left side more often than right.
• Psychological symptoms may be reported, including nervousness, unreality, disorientation, or feeling spacey.
• Hyperventilation syndrome is commonly misdiagnosed and can often be diagnosed with the hyperventilation provocation test.
According to a consensus definition, "hyperventilation syndrome is a syndrome characterized by a variety of somatic symptoms induced by physiologically inappropriate hyperventilation and usually reproduced in whole or in part by voluntary hyperventilation" (48). Acute hyperventilation with obvious tachypnea accounts for about 1% of all cases of hyperventilation (52). The other 99% of cases are due to chronic hyperventilation where there may be a modest increase in respiratory rate or tidal volume, which may not even be apparent to the patient or a medical observer.
The symptoms of hyperventilation syndrome have been recognized for at least 125 years. In 1871, Da Costa published a paper, On Irritable Heart; a Clinical Study of a Form of Functional Cardiac Disorder and its Consequences, describing 300 Union soldiers in the American Civil War with a mysterious illness (14). He felt the condition could be seen in private practice as well. Symptoms included palpitations, chest pain, shortness of breath or oppression on exertion, indigestion, abdominal distention, and diarrhea. Headache, giddiness, disturbed sleep, and dizziness were "all indicative of disturbed circulation in the cerebro-spinal centres." Da Costa reasoned that "the heart has become irritable, from its over-action and frequent excitement...." During World War I, similar symptoms often associated with fatigue were also attributed to cardiovascular dysfunction and described as "soldier's heart" (49) or "neurocirculatory asthenia" (46). In contrast, Gowers used the terms "vagal" and "vaso-vagal" for these symptoms, which could include numbness and tingling of the extremities (28).
In 1922, Goldman was the first to make the connection between "forced ventilation" and tetany and postulated that the tetany was due to alkalosis (26). Kerr and colleagues introduced the term "hyperventilation syndrome," and they described the variety of symptom complexes caused by physical phenomena associated with anxiety states, which could often be reproduced in the examining room with the "hyperventilation test" (41; 42).
Lewis contended that acute and chronic hyperventilation syndrome occurred frequently and described the common and atypical presentations, pathophysiology, and therapy (47). He reported that paresthesias were occasionally asymmetrical and could even be unilateral. Tavel described patients with hyperventilation syndrome presenting with unilateral paresthesias at times associated with subjective unilateral weakness that involved the left side of the face and body more commonly than the right (72).
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