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March 27, 2021
Although BPPV accounts for the overwhelming majority of cases of positional vertigo, there are also other possibilities.
CPV is a rare cause of positional vertigo. It is especially common due to structural lesions in the cerebellum, especially the cerebellar nodulus and uvula (Lee et al, 2014). There are a number of potential causes -- CPV is nearly universal in persons with medulloblastoma, which is a tumor that arises in the cerebellar nodulus.
CPV is also somewhat common in the Arnold-Chiari malformation and the related disorder of basilar invagination, and after strokes, tumors or multiple-sclerosis lesions involving the brainstem or cerebellum area. There are numerous rare cerebellar degenerations that can also result in central positional vertigo.
Ordinarily this diagnosis is made by noting a positional vertigo, finding that it does not respond to exercises for BPPV, and then further investigation.
Concerning BPPV, posterior canal BPPV is rarely confused with CPV. On the other hand, the physical findings of anterior canal and lateral canal BPPV (non-PC BPPV) are less specific. Non-PC BPPV can be misidentified as CPV, and CPV can be misidentified as non-PC bppv.
We have had several cases in which lateral canal BPPV was initially diagnosed, and later on a brain tumor was discovered. In our opinion, imaging of every patient with vertigo is not needed, but if patients do not respond to the usual treatments effective for their diagnosis, then further imaging is reasonable. Lee et al (2014) reported six patients with ageotrophic DCPN having lesions of the cerebellar nodulus or vermis, and another two patients with a geotrophic nystagmus that had cerebellar lesions. Because the vestibular input circuitry sends a very large contingent of fibers to the cerebellum, it is not at all surprising that nearly any positional nystagmus can be caused by cerebellar lesions -- including strokes, tumors or MS among others.
Treatment of central positional vertigo, other than attempting to correct the cause, is not well worked out. Generally one attempts treatment with vestibular suppressants and centrally acting drugs. Vestibular rehab does not help central positional vertigo.
Benign recurrent vertigo
This is an episodic positional vertigo syndrome, first described by Slater (1979), and also by Cha et al (2008). It is thought to be a migraine variant. It resembles "cyclic vomiting", another migraine variant, but there is more nystagmus and less vomiting. Fortunately this is rare -- the ratio of this condition to "regular" BPPV is about 1:1000. The most salient features include:
- Positional vertigo
- No headache -- while attributed to migraine, actually "migraine headaches" are not required.
- Recurrences, somewhere between every 3 months and every 12 months.
- No response to physical therapy.
In the author's (unpublished) observations, both cyclic vomiting and BRV often respond to verapamil. However, in BRV, there generally is little enthusiasm about taking a medication all year long for 2 days of misery.
In one BRV patient that came in during their yearly spell, the author observed strong direction changing (geotrophic) horizontal positional nystagmus, as well as strong upbeating nystagmus in head-center supine position. This is not a lateral canal BPPV pattern (because of the upbeating nystagmus).
As can be imagined, this condition overlaps with other periodic vestibular conditions - - mainly migraine and Meniere's.
The best management is generally just to treat the symptoms and wait a few days. If it lasts longer than 2 days, one should consider lateral canal BPPV, and if it doesn't respond to physical therapy, other entities.
In this syndrome, mechanical compression of a normal or irritable 8th nerve is postulated to create vertigo. The general idea is reasonable enough but current diagnostic technology is not good enough yet to diagnose this syndrome. We don't think it is common.
Orthostatic hypotension (dizzy on standing)
This is not a vestibular syndrome, but rather a simple situation where blood pressure drops on standing. It is discussed in detail in the link above.
As the otoliths are gravity sensors, it follows that otolithic disorders should cause abnormal reactions to gravity.
Yagi has suggested that lateral canal BPPV is sometimes actually due to utricular damage (2001). This conclusion was based on the observation that geotrophic direction changing nystagmus is not directed in canal coordinates. While we accept Yagi's observations, the conclusion that the utricle is the generator seems somewhat tenuous. Follow this link for more information about the utricle.
In hydrops, which is universal in Meniere's disease as well as common in the general population (about 10% on autopsy), the otolithic organs are distended. Follow the links above for more.
The above two images illustrate a patient who has no horizontal canal function on step responses to 100 deg/sec, but powerful horizontal nystagmus on positional testing. The data is very clear that he has bilateral vestibular impairment. How can this happen, given that there is no central positional nystagmus ?
After a severe vestibular disturbance, where parts of inner ear function is lost, the brain attempts to compensate. Sometimes this involves using of motion sensors in the inner ear for a different purpose than the original one. Along these lines, occasionally patients are encountered with "impossible" nystagmus. For example, bilateral vestibular loss, and strong horizontal positional nystagmus. If one has no inner ear function, there should be no positional nystagmus either.
A reasonable explanation for this is that there may be sparing of the utricle, which is used in an attempt to substitute for the lateral canals. This idea was brought up in 1989 by Arai et al, after experimental work in monkeys where the lateral canals were plugged. Given that the innervation and vascular supply of the utricle and superior canal is shared, one would think that it would be very rare for someone to selectively damage both lateral canals, but spare their utricle.
With respect to disorders in which there is a mismatch of endolymph and cupula density, the most commonly encountered is positional alcohol nystagmus (PAN). Commonly, when people imbibe a fair amount of an alcoholic beverage, they discover that upon lying down a strong vertigo ensues. This is caused by a difference in the rate that alcohol (which is lighter than water) enters the cupula of the inner ear compared to the endolymph.
We have seen a case in which we suspected that pneuomolabyrinth (air in the inner ear) caused a positional nystagmus. This was a case of a man with a temporal bone fracture.
Similar syndromes occur in situations where the cupula is weighted down (e.g. cupulolithiasis), and perhaps also in situations where there is an alteration of the density of the endolymph by disease (i.e. Waldenstrom's macroglobulinemia, and perhaps autoimmune disorders). This possibility has not been considered in detail in the otologic literature.
One might conjecture after a partial vestibular nerve injury, such as post vestibular neuritis or acoustic neuroma surgery, recovery and rewiring might occur. If this happened, one sensory organ (i.e. the utricle), might become miswired and end up innervating other parts of the vestibular apparatus.
Abberant regeneration is often seen in injuries of the facial nerve, for motor fibers. It is not something reported for sensory systems however. This might be a convenient explanation for sensory mix-ups in the vestibular system. Although attractive because it would provide another class of explanations, so far, this situation has not been documented in any experimental model.
Hearing has positional modulation to a lesser extent than does vertigo. Low-CSF pressure syndrome may cause hearing to be reduced on standing.
It may be possible for people with gastroesophageal reflux to have reduced hearing on lying flat, as well as serous otitis media from reflux (Heavner et al, 2001; Tasker et al, 2002).
Occasionally persons with sleep-apnea develop positional hearing syndromes, presumably related to pressurization of the middle ear during sleep, making it a variant of barotrauma.