Expansion
Three divisions tested separately, plus the corneal reflex
Expansion
The test: light touch with cotton wool, then pinprick, comparing the two sides in each division, with the eyes closed.
- V1 ophthalmic: forehead
- V2 maxillary: cheek
- V3 mandibular: jaw, sparing the angle of the mandible, which is supplied by C2 and C3
The angle of the mandible is the useful landmark: sensory loss over the whole face including the angle is not anatomically trigeminal and suggests a functional disorder.
Corneal reflex: touch the cornea, not the sclera, with a wisp of cotton wool from the side, with the patient looking away. The afferent limb is V1 and the efferent is VII, so both eyes should blink.
- Absent direct and consensual on stimulating one eye: trigeminal (afferent) lesion
- Absent on the stimulated side only, with the other eye blinking: facial (efferent) lesion on the stimulated side
An early absent corneal reflex is a classic sign of a cerebellopontine angle lesion, such as a vestibular schwannoma, alongside deafness and facial weakness.
Patterns of loss
- All three divisions: a lesion at or proximal to the ganglion
- One division: a peripheral branch lesion
- Onion skin pattern, with loss around the mouth and nose sparing the periphery or the reverse, indicates a brainstem spinal trigeminal nucleus lesion
- Dissociated loss, with pain and temperature lost but light touch preserved, also localises to the brainstem, as in lateral medullary syndrome