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Abnormalities of Masseteric Inhibitory Reflex in Hereditary Geniospasm: Evidence for a Brainstem Myoclonus
Author(s) -
Macerollo Antonella,
Saifee Tabish A.,
Kassavetis Panagiotis,
Pilurzi Giovanna,
Schneider Susanne A.,
Edwards Mark J.,
Bhatia Kailash P.
Publication year - 2015
Publication title -
movement disorders clinical practice
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.754
H-Index - 18
ISSN - 2330-1619
DOI - 10.1002/mdc3.12097
Subject(s) - brainstem , corneal reflex , reflex , myoclonus , inhibitory postsynaptic potential , spontaneous recovery , silent period , pathophysiology , neuroscience , anesthesia , medicine , psychology , stimulation , transcranial magnetic stimulation
We studied two unrelated families with several members suffering from geniospasm. Here, we aim to clarify the pathophysiology underlying the hereditary geniospasm through testing of brainstem excitability by the recovery cycles of the blink reflex ( BR ) and the masseteric inhibitory reflex ( MIR ). The R2 component of the BR and the SP 2 component of the MIR and their recovery cycle were analyzed in 3 patients and 8 healthy, age‐matched subjects as the control group. Patients with geniospasm exhibited a different excitability of the BR, compared to the control, group, as shown by the larger R2 component area of BR in controls than patients. Notably, the mean recovery index was 0.61 ± 0.19 in geniospasm patients and 0.40 ± 0.15 in controls ( P ≤ 0.05). Interestingly, the recovery cycle of the MIR showed a loss of inhibition in both patients studied, as indicated by the behavior of the SP 2 component. Our cases showed a partial impairment of the activity of brainstem inhibitory interneurons, indicated by the abnormal recovery cycle of MIR . These results would implicate a mechanism akin to brainstem myoclonus for the generation of geniospasm.