Short latency trigemino-sternocleidomastoid response in muscles in patients with spasmodic torticollis and blepharospasm.
OBJECTIVE
To further elucidate the pathogenesis of focal dystonias.


METHODS
Short latency responses can be recorded in tonically active sternocleidomastoid muscles after stimulation of the infraorbital branch of the trigeminal nerve. Such trigemino-sternocleidomastoid response consists of a bilateral positive/negative wave in the average of unrectified surface EMG, corresponding to a short period of inhibition of motor unit firing. This brain stem reflex was investigated in 10 normal subjects, in 16 patients affected by spasmodic torticollis (ST) and in 10 patients with blepharospasm (BSP).


RESULTS
All ST patients presented abnormalities of SCM responses after infraorbital nerve stimulation. The abnormalities were bilateral in all but one of the patients and were independent from previous treatment with botulinum toxin. No BSP patients showed alterations of this reflex.


CONCLUSIONS
Abnormalities of brain stem interneurons which are responsible for oligosynaptic exteroceptive suppression reflexes occur specifically in ST. These findings further support the relevance of sensory inputs in the determinism of focal dystonias.
Quartarone
A
A
Institute of Neurological and Neurosurgical Sciences, University of Messina, 98125, Messina, Italy. angelo.quartarone@unime.it
Girlanda
P
P
Di Lazzaro
V
V
Majorana
G
G
Battaglia
F
F
Messina
C
C
D000328:Adult; D001764:Blepharospasm / Q000503:physiopathology*; D004421:Dystonia / Q000503:physiopathology; D004576:Electromyography; D006801:Humans; D008875:Middle Aged; D009334:Neck Muscles / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D014103:Torticollis / Q000503:physiopathology*; D014276:Trigeminal Nerve / Q000503:physiopathology*