Table 3 Brainstem reflexes neuroanatomical and clinical description
Reflex | Examination technique | Normal response | Afferent pathway | Brainstem centers | Efferent pathway |
|---|---|---|---|---|---|
Physiological reflexes | |||||
 Pupillary light reflex | Response to light | Direct and consensual myosis followed by mydriasis | Retina, optic nerve, chiasma, optic tract | Pupillo-constrictor: midbrain, pretectal olivary nucleus, Edinger-Westphall nucleus Pupillo-dilator: posterior-lateral hypothalamus, cervical ganglion, trigeminal ganglion, abducens | Sympathetic fibers of cranial nerve III (oculomotor) |
 Cilio-spinal | Latero-cervical nociceptive stimulation | Uni- or bilateral irido-dilatation | Sensory ascending pathways to centro-spinal centers | Midbrain | Cranial nerve III |
 Fronto-orbicular | Glabellar percussion | Eyes closing | Cranial nerve V (trigeminal) | Pons | Cranial nerve VII (facial) |
 Oculocephalic | Turn head from side to side | Eyes move conjugately in direction opposite to head | Semicircular canals, Cranial nerve VIII (oculovestibular) | Pons, nucleus vestibularus, nucleus abducens | Cranial nerves III (oculomotor) and VI (abducens) |
 Oculovestibular | Irrigate external auditory canal with 50 ml of cold water | Nystagmus | |||
 Corneal | Stimulation of cornea with saline drops | Eyelid closure | Cranial nerve V (trigeminal) | Pons, trigeminal and facial nuclei | Cranial nerve VII (facial) |
 Grimace/masseterian | Deep pressure on nail bed, supraorbital ridge, or temporo-mandibular joint | Facial grimace and limb movement | |||
 Cough reflex | Stimulation of the carina with a suction tube | Cough | Cranial nerve IX (Glossopharyngeal) and X (vagal) | Medulla, nucleus tractus solitarius | Cranial nerve IX (glossopharyngeal) and X (vagal) |
 Gag/pharyngeal reflex | Stimulation of the soft palate | Symmetrical rise of soft palate gag reflex | |||
 Oculocardiac | Ocular globe compression | Decrease in heart rate | Cranial nerve V (trigeminal) | Pons, medulla | Cranial nerve X (vagal) |
Primitive reflexes | |||||
 Palmo-mental | Pressure of the thenar eminence with a thin stick | Single twitch of the ipsilateral mentalis muscle | Posterior column-medial lemniscus pathway | Pons | Cranial nerve VII (facial) |
 Corneo-mandibular | Corneal stimulation | Contralateral deviation of the jaw | Cranial nerve V (trigeminal) | Pons | Cranial nerve VII (facial) |
Other syndromes | |||||
 Internuclear ophthalmoplegia (see Fig. 1) | Oculomotricity testing Can be observed during oculocephalogyric or oculovestibular tests | Disconjugate lateral gaze with a preserved convergence | Lesion of the medial longitudinal fasciculus | Connects the sixth nucleus with the contralateral third nucleus |  |
 Claude Bernard-Horner’s syndrome | Ptosis, myosis, enophtalamos, anhidrosis |  | Sympathetic pathway injury |  |  |
 Vertical nystagmus, skew deviation |  |  | Midbrain or medulla injury |  |  |
 Ocular bobbing |  |  | Pons injury |  |  |