Timothy C. Hain, M.D. • Last modified on July 20, 2019
Neuropathies are conditions that cause disorders of nerves. The vestibular nerve is a nerve (of course). Therefore neuropathies can damage the vestibular nerve. There are two general types of neuropathy -- axonal and demyelinating (see below).
In neurology, neuropathies and ganglionopathies are often lumped together, because both impair sensation.
|Ganglionopathy||Rare dorsal root syndromes associated with cancer.|
There are two broad categories of neuropathies - -axonal and demyelinating. Examples of these are provided above. There are also disorders of the sensory neurons that sprout nerves. These generally "live" in ganglions, which are located close to the spinal cord, or close to the nerve itself. The vestibular nerve also has a ganglion, and thus ganglionopathies can damage the vestibular ganglion as well.
The vestibular nerve is one of the cranial nerves -- one of the nerves that is locate in the head (cranium). Cranial nerves, generally speaking, are much shorter than nerves in the limbs such as the nerves that go to the fingers or toes. This means that it is less vulnerable to "length dependent" processes (such as axonal neuropathies) than longer nerves. Cranial nerves, are especially vulnerable to ganglionopathies as well as demyelinative processes. They are not especially vulnerable to axonal neuropathies. According to Buetti and Luxon , the crainal nerves most frequently affected by neuropathic disorders are the optic nerve, trigeminal and facial nerve. Examples here might be optic neuritis, trigeminal neuralgia, and Bells palsy.
Certain common inner ear disorders, such as "vestibular neuritis (or neuronitis)", are caused by damage to the vestibular nerve, generally one or the other.
Here we intend to review what is known about neuropathies that affect all or at least most of the nerves in the body, and that also have imbalance or dizziness. Most of this is rather obscure material.
CIDP is a common autoimmune peripheral neuropathy, mainly known for symptoms of weakness and sensory loss. It is a demyelinating neuropathy, meaning that it can affect both long and short nerves. Of course, these patients have imbalance because they usually have difficulty feeling their feet or joints above their feet.
One would THINK that CIDP would mainly affect the longer nerves that have more targets to be demyelinated, but might also occasionally affect shorter nerves such as cranial nerves. One would THINK that both the vestibular nerve and the cochlear (hearing nerve) would be equally vulnerable. Furthermore, one would THINK that balance would be impaired in all CIDP patients (because they can't feel their feet), whether or not they had any vestibular issues.
Regarding vestibular or cochlear nerve damage:
Regarding balance impairment, impairment of balance in neuropathy is "common knowledge" and not worth reviewing here.
- Akdal et al (2018) reported on 21 patients with CIDP. Their vestibular measure was the VHIT test. Of their 21 patients, 3 had low gain (defined as anything below the lower limit of normal) in all 6 semicircular canals. This suggests that about 1/7 patients with CIDP have significant vestibular damage, presumably from demyelination of their vestibular nerves. In support of this supposition, is that several of the same patients also had weakness of other cranial nerves.
- Blanquet et al (2018) reported on another 21 patients, with a variety of inflammatory (autoimmune) neuropathies (CDIP, Guillain-Barre, anti-MAG, multifocal motor), not necessarily all demyelinating. Again, their technique was to use the VHIT test, combined with VEMP tests. These authors counted any abnormality as a positive (i.e. any vertical canal pair). This was basically a fishing expedition, looking for and reporting everything they could find, using a large number of individual measures. Unsurprisingly, they did find a variety of miscellaneous impairment, which did not correlate with their subjective dizziness. This study has relatively little to say, because of the design that was very inclusive.
- Frohman et al (1996) described typical bilateral vestibular loss in a single patient with CIDP, accompanied by enhancement of cranial nerve VIII.
Cerebellar Ataxia-Neuropathy-Vestibular areflexia, or CANVAS, is a rare disorder, tentatively attributed to a gangliopathy. Perhaps a variant of Freidriechs ataxia. As there are three separate reasons for unsteadiness, persons with CANVAS are extremely unsteady. It is discussed in great detail here. It is puzzling that the cochlear (spiral) ganglion appears to be spared in CANVAS.
FA is a common hereditary ataxia, caused by an expansion of a GAA repeat. Friedreichs is discussed in greater detail here.
Charcot Marie tooth disease is another slowly progressive neuropathy, usually familial. It has been renamed as HMSN (hereditory motor and sensory neuropathy). There are several genetic variants. HMSN I is the demyelinating type, HMSN II is the axonal type, and HMSN III-IV are recessive types. Some of these patients also have vestibular problems.
Buetti and Luxon (2014) reviewed the confusing situation with respect to vestibular function in various peripheral neuropathies. While one would expect very little vestibular impairment, the reports are "all over the map". In general, the reports are much higher than expected. We feel that this is due to research methodology in which patients are subjected to numerous tests, and anything wrong on just one paramater is considered "abnormal". This is the "Bonferonni" problem.
Palla et al (2009) reported vestibular impairment in 81% of patients with axonal PN, and 63% of patients with demyelinating PN. This is much higher than other workers. More study is needed.
Miscellaneous vestibular deficits have been reported in several studies (see Buetti and Luxon, 2014). It is certainly not universal. Again, rather peculiarly, some workers suggest that there is vestibular "involvement" in rather large numbers of patients. This is certainly not our experience.
Sarcoidosis, is a mysterious granulomatous disorder, that can involve nerves. Patients with sarcoid have developed vestibular nerve damage. It is not clear whether or not sarcoid has a particular fondness for attacking the vestibular nerve, as opposed to other parts of the body. Probably not.
There is an association between certain antibiotics, such as fluroquinolones, and dizziness. One possible mechanism is neuropathy. As of 2019, this was just a conjecture, not proven.