MenieresNSW.org.au
No menu? Click on this link to go to our home page: http://www.menieresnsw.org.au/
Loose rocks in your head!
Benign Paroxysmal Positional Vertigo (BPPV) is a unique form of dizziness causing a transient rotational vertigo on lying down or rolling over in bed. The condition was first described by Baranay in 1921 and is the most common cause of true rotational vertigo in adults. It is estimated that 20% of all vestibular complaints are due to BPPV.
To understand the cause of BPPV, we need to understand a little of the function of the semi circular canals. We have three semi circular canals in each inner ear. Each semi circular canal is set at right angles to another, and they are designed to detect angular acceleration. This means that rather than detecting the force of gravity and therefore knowing which way is up (a job performed by the utricle and saccule of the inner ear), the semi circular canals detect movement of our head in any direction or plane.
The way that the semi circular canals detect movement is very simple. Within each semi circular canal is a movement detection mechanism, which consists of a small crest upon which sits a delicate membrane that partially closes the lumen of the semi circular canal. This is called the cupula. Each semi circular canal is fluid filled and when the head is turned, the pressure of the fluid pushes or pulls against the cupula, causing deflection of the fine membrane. The deflection is detected by nerve cells, which send signals to the cerebellum and brain stem indicating that movement has occurred. An analogy might be the movement that we see in seaweed attached to a rock in the ocean as the water moves back and forth.
In BPPV, the cupula of the posterior semi circular canal behaves and moves abnormally. It seems that this abnormal movement is due to small pieces of calcium carbonate material, which may be either attached to the cupula of the posterior semi circular canal, or alternatively floating free in the lumen of the posterior semi circular canal. The origin of the small stones is unknown, but they could be shaken lose from the otolith organ which resides in the utricle and saccule of the inner ear.
Why the small deposits of calcium carbonate fall off and end up in the posterior semi circular canal or on the cupula of the semi circular canal is not known. Certainly BPPV is commonly seen after vestibular neuronitis, a condition which causes severe rotatory vertigo, nausea and vomiting unassociated with hearing loss which may last for two to three days and only gradually remits over a period of a week. Other conditions that have been related to the onset of BPPV include head trauma, Ménière's Disease, and following ear surgery especially stapedectomy. There is also clearly spontaneous BPPV that comes on without any of these conditions.
People with BPPV have a fairly predictable story. They typically have few symptoms when they are upright and moving around, but on lying down or rolling over in bed onto the affected ear, severe rotational vertigo begins after a brief one to five second latency period. The vertigo may last from ten to thirty seconds, stops on moving out of the provocative position, and generally happens less if the provocative position is assumed a number of times in succession. There is no associated hearing loss or tinnitus with BPPV.
Benign Paroxysmal Positional Vertigo can assume an acute, remitting, or chronic course. The acute type is usually unheralded, and lasts for days to weeks with spontaneous remission. The remitting type is similar to the acute, but recurrent episodes of acute symptoms may occur periodically over a period of months to years. The chronic type which is very uncommon, is related to persistent symptoms of BPPV of constant severity without remission.
The diagnosis of BPPV is usually suspected when the history of true rotational vertigo on lying down or rolling over is given. The condition is diagnosed clinically by a manoeuvre called the Hallpike Test. In this test, the patient is rapidly taken from the sitting position with the head upright to the lying position with first one and then the other ear down. Typically after a short latent period, the patient experiences rotational vertigo. The diagnosing doctor will notice that the patient's vertigo is accompanied by a rotatory form of nystagmus (involuntary movement of the eyes). The episode can be terminated by returning the patient to the upright position.
An audiogram is required to ensure there is no other otologic pathology. Generally, further investigations are not required.
The treatment of BPPV is fortunately successful and reasonably easy. The acute and acute relapsing forms of BPPV will spontaneously remit over days to weeks. More recently, particle repositioning manoeuvres have been described whereby the small stones of calcium carbonate that are in the posterior semi circular canal can be relocated into another part of the inner ear insensitive to these particles, by a rolling manoeuvre usually accomplished on the physician's bench. There are several particle repositioning manoeuvres currently in use, which vary from swinging the patient's head through a 180o arc to a more gradual repositioning manoeuvre with the head being taken through a 270o circle, often with a vibrator applied to the head to help dislodge the particles.
Chronic BPPV can also be treated successfully. Recently an operation to insert a partition into the posterior semi circular canal has been proposed and successfully utilised to stop the movement of fluid within the posterior semi circular canal and therefore stop the effect of particles moving within the canal on the cupula. Finally, if all else fails, section of the nerve supply leading from the posterior semi circular canal (singular neurectomy) or section of the entire vestibular nerve (vestibular neurectomy) have been performed.
Fortunately, the vast majority of patients settle spontaneously or with the help of particle repositioning manoeuvres.
The clinical condition of benign paroxysmal positional vertigo is a fascinating one, so if your doctor tells you that he thinks you have loose rocks in your head, you'll know that he's thinking of BPPV!
Dr. Glen Croxson
Eastwood NSW