Value of homonymous and heteronymous monosynaptic reflexes in the diagnosis and follow up of cervical spinal injuries

Needle electromyographic examination constitutes the only neurophysiologica l test used routinely to assess the integrity of proximal nerve pathways. A heteronymous reflex, with a latency consistent with a monosynaptic pathway , can be evoked in the contracting biceps brachii muscle by stimulation of the median nerve at the elbow. This reflex response provides a complementar y technique to the biceps and supinator jerks for accessing the C-5/C-6 mot oneuron pool because its afferent limb involves the median nerve and the C- 5/C-6 posterior roots. Three cases are described to illustrate the clinical value of this heteronymous monosynaptic reflex of biceps brachii and of co nventional H reflexes in the diagnosis and follow-up of lesions involving t he C-5/C-6 segments. Reflex function can be assessed for most spinal segmen ts innervating the upper and lower limbs, thus allowing both objective conf irmation of the clinical findings and documentation of changes over time.