Short and long interval cortical inhibition in patients with Unverricht-Lundborg and Lafora body disease.
Myoclonus has different clinical and neurophysiological features in patients with Unverricht-Lundborg (ULD) and Lafora body disease (LBD), probably because of a different cortical hyperexcitability profile. To investigate the role of intracortical inhibition in such different presentations, we used paired-pulse transcranial magnetic stimulation (TMS) in ten ULD and five LBD patients, all with a positive molecular diagnosis. All of the patients were treated with antiepileptic drugs (AEDs). In comparison with healthy subjects, both patient groups had significantly defective short intracortical inhibition (SICI), however LBD patients, but not ULD and healthy subjects, had a clear inhibition at ISI 6 ms and ISI 10 ms. Moreover, defective long interval cortical inhibition (LICI) was found in LBD but not ULD patients. The substantial reduction in SICI suggests that both ULD and LBD patients have impaired inhibitory interneuron pools which are involved in the generation of cortical reflex myoclonus, whereas the inhibition found in LBD patients at ISI 6 and 10 ms, as well the reduced inhibition found at long intervals, suggest a more complex circuitry dysfunction possibly involving both excitatory and inhibitory systems. These findings are probably related to the high epileptogenic propensity characterizing LBD with respect to ULD and to the more severely distorted neuronal network resulting from the pathogenesis of LBD.
Canafoglia
Laura
L
Dept. of Neurophysiopathology and Epilepsy Centre, IRCCS Foundation Carlo Besta Neurological Institute, Via Celoria 11, 20133 Milano, Italy. canafoglia@istituto-besta.it
Ciano
Claudia
C
Visani
Elisa
E
Anversa
Paola
P
Panzica
Ferruccio
F
Viri
Maurizio
M
Gennaro
Elena
E
Zara
Federico
F
Madia
Francesca
F
Franceschetti
Silvana
S
D000328:Adult; D000368:Aged; D002540:Cerebral Cortex / Q000503:physiopathology*; D005260:Female; D006801:Humans; D020192:Lafora Disease / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology; D009433:Neural Inhibition; D011930:Reaction Time; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D020194:Unverricht-Lundborg Syndrome / Q000175:diagnosis / Q000503:physiopathology*