Brief episodes of hemiplegia in a patient with multiple sclerosis
A 43 year old man presented with repeated episodes of right sided hemiplegia over a six month period. These would occur from once a day to once every three to four weeks and last only a few seconds before returning to normal. There were no associated sensory symptoms. There was no facial involvement, headache, vertigo or other cranial nerve signs or symptoms. Physical examination was normal. Magnetic resonance imaging of his brain revealed multiple areas of hyperintensity on T2 consistent with demyelination. A lesion was noted at the left pontomedullary junction as well as a number of small lesions within the cervical spinal cord. EEG was normal. Visual evoked potentials showed a delayed P100 response from the left eye, and sensory and motor evoked potentials were abnormal from the right side. Vascular studies were normal. The patient was treated with sodium valproate 200 mgs bd with good effect. The symptoms ceased completely. Cessation of drug resulted in the recurrence of symptoms, which then did not recur with reinstitution of the drug. This is a case of very brief, paroxysmal episodes of hemiplegia in a patient with probable multiple sclerosis. It is suggested that the paroxysmal phenomena in MS are caused by a transversely spreading ephaptic activation of axons within a demyelinated lesion in fibre tracts in the central nervous system. Alternatively, they may be related to release of inflammatory soluble factors, dysfunction of ion channels and accumulation of extra-cellular potassium or epileptic activity arising from an MS plaque. In this patient the symptoms arose most likely from abnormal excitability within the pontomedullary plaque on the left side. Although paroxysmal dystonia, dysarthria, ataxia, paraesthesia, diplopia ,itching and tonic seizures have been described previously, to our knowledge transient hemiplegia of such brief duration and responding to anticonvulsants has not.