Decreased cortical inhibition and yet cerebellar pathology in 'familial cortical myoclonic tremor with epilepsy'.
Cortical hyperexcitability is a feature of "familial cortical myoclonic tremor with epilepsy" (FCMTE). However, neuropathological investigations in a single FCMTE patient showed isolated cerebellar pathology. Pathological investigations in a second FCMTE patient, reported here, confirmed cerebellar Purkinje cell degeneration and a normal sensorimotor cortex. Subsequently, we sought to explore the nature of cerebellar and motor system pathophysiology in FCMTE. Eye movement recordings and transcranial magnetic stimulation performed in six related FCMTE patients showed impaired saccades and smooth pursuit and downbeat nystagmus upon hyperventilation, as in patients with spinocerebellar ataxia type 6. In FCMTE patients short-interval intracortical inhibition (SICI) was significantly reduced. Resting motor threshold, recruitment curve, silent period, and intracortical facilitation were normal. The neuropathological and ocular motor abnormalities indicate cerebellar involvement in FCMTE patients. Decreased SICI is compatible with intracortical GABA(A)-ergic dysfunction. Cerebellar and intracortical functional changes could result from a common mechanism such as a channelopathy. Alternatively, decreased cortical inhibition may be caused by dysfunction of the cerebello-thalamo-cortical loop as a result of primary cerebellar pathology.
van Rootselaar
Anne-Fleur
AF
Department of Neurology and Clinical Neurophysiology, University of Amsterdam, Amsterdam, the Netherlands. a.f.vanrootselaar@amc.uva.nl
van der Salm
Sandra M A
SM
Bour
Lo J
LJ
Edwards
Mark J
MJ
Brown
Peter
P
Aronica
Eleonora
E
Rozemuller-Kwakkel
Johanna M
JM
Koehler
Peter J
PJ
Koelman
Johannes H T M
JH
Rothwell
John C
JC
Tijssen
Marina A J
MA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000927:Anticonvulsants / Q000627:therapeutic use; D002526:Cerebellar Diseases / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D002540:Cerebral Cortex / Q000473:pathology* / Q000503:physiopathology; D004594:Electrophysiology; D004831:Epilepsies, Myoclonic / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D019054:Evoked Potentials, Motor / Q000502:physiology; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000209:etiology; D010375:Pedigree; D011698:Pursuit, Smooth / Q000502:physiology; D012438:Saccades / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014202:Tremor / Q000473:pathology* / Q000503:physiopathology
D000927:Anticonvulsants