Alterations of the 8th CN
- Which has the longest central myelin portion of all CNs, from brainstem to internal auditory canal,
- May be at the origin of tinnitus (cochlear nerve) and vertigo (vestibular nerve).
- Mechanisms are pathological insult(s), of any kind, lesions being responsible for peripheral deafferentation followed by central synaptic reorganization, similar to what can be observed at the origin of many types of neuropathic pain.
- A number may be related to NVC, the diagnosis of which is sometimes difficult to ascertain.
Compression due to left intra-IAC vascular loop
- Compression of the vestibular portion of CN8 can cause irritation causing a syndrome of vestibular paroxysmia where patients have symptoms including
- Vertigo (rotational, short duration)
- Motion intolerance.
- Several other processes cause these symptoms through damage to the nerve:
- Via vestibular neuritis, tumour, radiation, surgical iatrogenic damage
Aetiology
- Neurovascular compression syndrome of CN8 is more controversial
- Most commonly from AICA (75%)
Pathophysiology
- Transition zone: 11mm. Compression typically in the IAC. Site of compression can vary along this distance.
- CN8 has a long cisternal segment from brainstem to IAC
Symptoms
- Tinnitus from compression cochlear nerve (caudally), vertigo from compression of vestibular nerve (rostroventral)
Treatment
- Medical: mainly carbamazepine
- Surgical: MVD in intractable cases
Made with Bullet