title: Reduced brain stem excitability in mitochondrial myopathy: evidence for early detection with blink reflex habituation studies.
abstract: Blink reflex (BR) was studied in 17 patients with histochemically and genetically confirmed mitochondrial myopathy (MM). Fourteen patients had chronic progressive external ophthalmoplegia (CPEO) associated with a mild to moderate craniosomatic myopathy without any symptoms or signs of central nervous system (CNS) involvement, 2 myoclonic epilepsy with ragged red fibers syndrome, and 1 Kearns-Sayre syndrome. The mean latencies of the early (R1) and late (R2) responses were prolonged (P < 0.01 and P < 0.001, respectively), and the corresponding amplitudes decreased (P < 0.001). Increased habituation of the reflex was clearly observed in 10 out of 14 patients tested (71.4%), 9 of whom presented CPEO. These findings suggest that the brain stem reticular network is in a state of basal inhibition which is presumably due to a subclinical impairment of the cerebral cellular metabolism. Multimodal evoked potentials revealed abnormalities suggestive of CNS involvement in 7 out of 17 patients (41.2%), 4 of whom had CPEO. These observations document the validity of BR in detecting clinically silent brain stem impairment in patients with apparently pure MM and provide important clues for a further understanding of the underlying pathophysiology.
authors.affiliation: Department of Clinical Neurophysiology and Epilepsies, St Thomas' Hospital, London, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Koutroumanidis
authors.forename: A
authors.initials: A
authors.lastname: Papadimitriou
authors.forename: E
authors.initials: E
authors.lastname: Bouzas
authors.forename: T
authors.initials: T
authors.lastname: Avramidis
authors.forename: P
authors.initials: P
authors.lastname: Papathanassopoulos
authors.forename: R S
authors.initials: RS
authors.lastname: Howard
authors.forename: T
authors.initials: T
authors.lastname: Papapetropoulos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001767:Blinking; D001933:Brain Stem / Q000503:physiopathology*; D004576:Electromyography; D004594:Electrophysiology; D016057:Evoked Potentials, Auditory, Brain Stem; D005073:Evoked Potentials, Somatosensory; D005074:Evoked Potentials, Visual; D005260:Female; D006185:Habituation, Psychophysiologic; D006801:Humans; D008297:Male; D008875:Middle Aged; D017240:Mitochondrial Myopathies / Q000503:physiopathology*; D012016:Reference Values