Brainstem reflexes are enhanced following severe spinal cord injury and reduced by continuous intrathecal baclofen.
OBJECTIVE
Plastic changes in the human central nervous system can occur at multiple levels, including circuits rostral to the lesion level in spinal cord injury (SCI). GABA is the most important inhibitory neurotransmitter in the brain. The authors hypothesized that one of the consequences of plasticity in SCI patients could be enhancement of brainstem reflexes, and they investigated the effect of continuous intrathecal baclofen (CITB) on such enhancement.


METHODS
The authors studied the early ipsilateral component R1 and the late component R2 of the blink reflex (BR), jaw jerk, masseter silent period (MSP), and auditory startle response (ASR) in 9 SCI patients without baclofen and in 8 with CITB. Nine healthy volunteers served as controls.


RESULTS
The amplitude of R1 of BR was significantly smaller in patients with CITB than in the other groups. The area of R2 of BR and of the ASR recorded in the orbicularis oculi, sternocleidomastoid, and biceps brachii muscles were significantly larger in SCI patients without baclofen than in controls, whereas there was no difference between patients with CITB and controls. The MSP magnitude was significantly larger in patients with CITB as compared with those without baclofen.


CONCLUSIONS
The enhancement of brainstem reflexes in SCI patients may be due to plastic changes at the brainstem level after SCI. The significant reduction in response size in patients with CITB in comparison with patients without baclofen suggests that the enhancement of brainstem reflexes may be due to decreased GABAergic activity and that CITB is effective in reducing abnormal brainstem hyperexcitability.
Kumru
Hatice
H
Department of Neurology, Instituto Guttmann, Badalona, Spain. hkumru@guttmann.com
Kofler
Markus
M
Valls-Solé
Josep
J
Portell
Enric
E
Vidal
Joan
J
D000328:Adult; D019540:Area Under Curve; D001418:Baclofen / Q000008:administration & dosage / Q000627:therapeutic use*; D001933:Brain Stem / Q000187:drug effects / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D018755:GABA Agonists / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D007278:Injections, Spinal; D008297:Male; D008875:Middle Aged; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000188:drug therapy* / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
D018755:GABA Agonists; D001418:Baclofen