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We report the use of lamotrigine to treat paroxysmal kinesigenic choreoathetosis. Paroxysmal cases of kinesigenic choreoathetosis were first described in 1962 by Lishmanet al 1 and the term “paroxysmal kinesigenic choreoathetosis” was first coined by Kertesz2 in 1967. Recently, a more universal and potentially useful classification of these disorders has been proposed amending the terminology to “paroxysmal kinesigenic dyskinesia”.3 However, we have used the more familiar terminology for our patient as it is more precise. The clinical features of paroxysmal kinesigenic choreoathetosis have been reviewed by Marsden and Luders.4
There is a male preponderance of the condition with about 50% of cases inherited as an autosomal dominant trait, the rest being sporadic. Attacks are precipitated by sudden movements or startle and may be unilateral, bilateral, or affect alternate sides. Often the cause is idiopathic but a few cases have been attributed to multiple sclerosis. There has been no clear evidence for seizure activity in this disorder even though the condition is very responsive to antiepileptic drugs such as phenytoin and carbamazepine.4
A 13 year old boy of unrelated parents and with no family history of neurological disorder presented with a 6 month history of muscle spasms affecting the left side of his body. Close questioning indicated that his symptoms were brought on during the initiation of sudden movements (such as starting to run) and manifested as spasm of the left side of the face and flexor spasm of the left arm and left leg. There were no premonitory symptoms and consciousness was normal during the attack. Attacks lasted for a few seconds only and he felt perfectly well afterwards. Neurological examination was normal. Brain MRI was normal and three EEGs performed over the course of the next year were all normal. There were no biochemical or haematological abnormalities; copper studies were normal. A diagnosis of paroxysmal kinesigenic choreoathetosis was made. He was allergic to carbamazepine and did not respond to sodium valproate.
Lamotrigine (3,5-diamino-6-[2,3-dichlorophenyl]-1,2,4-triazine) is a use dependent blocker of voltage gated sodium channels and has a similar anticonvulsant profile to phenytoin and carbamazepine in animal models.5 Lamotrigine at a dose of 50 mg twice daily, completely abolished the involuntary movements. On two occasions, these returned on stopping lamotrigine and were abolished by reinstituting treatment. Our patient has taken this for over 2 years without ill effect. He now only experiences symptoms of paroxysmal kinesigenic choreoathetosis if he omits his medication. The response to lamotrigine may provide insight into the pathogenesis of the disease, suggesting that it may be caused by an ion channel defect; these are known to be responsible for some paroxysmal neurological conditions.6As far as we are aware, this is the first report of the successful use of lamotrigine to treat paroxysmal kinesigenic choreoathetosis.