THE ANATOMY OF THE EAR
The ear is conventionally and conveniently divided into three portions – the outer, the middle and the inner ears.
The inner ear is probably the most remarkably intricate piece of the body. Not only does it perform hearing by converting sound into electrical impulses that then travel along the hearing nerve to the brain [the acoustic N; auditory N; VIIIth or 8th nerve] but it also plays a major role in balancing. The balance portions of the inner ear [vestibular labyrinth] can detect acceleration of the head in any direction whether it be in a straight line [linear] or twisting and turning [angular]. The electrical signals that arise in response to head movement pass along the balance nerve [vestibular N; stato-acoustic N; VIIIth or 8th nerve] to the brain.
Below is a model of the human ear with the outer, middle and inner ears labelled
Below is a dissection I made of a human inner ear. I have left a thin bony shell (the bony labyrinth) over the finer structures of the cochlear and vestibular (balance) labyrinths – which together are called the membranous labyrinth.
The vestibular labyrinth comprises the utricle and saccule which detect straight line acceleration and the three semi circular canals (SCC) which detect angular acceleration. The semicircular canals are linked to the muscles that move the eyes and stimulation of one SCC results in movement of the eye in the opposite direction.
The vestibular labyrinth, like the cochlea, is stunningly sensitive and small changes can create major symptoms.
The human bony labyrinth:
A diagram of the human membranous labyrinth which contains the sensory cells of hearing and balance.
The sensory cells of the balance system are essentially the same in the two parts that detect linear or angular movements. The cell body is either flask shaped or cylindrical and has hair like structures projecting form their upper surfaces. Deflection of the hair bundle in one direction results in stimulation and an increased neural out put whilst deflection in the opposite direction results in suppression and a reduced output. Thus the cells have “polarity” in that they can “tell” which way they are being moved.
The sensory cells are essentially the same in the two portions of the inner ear – it is the way in which they are stimulated that allows them to detect linear or angular movements.
Below are two high power views of the human utricle showing the crystalline otoconia in relation to the long “hairs” (stereocilia) that project from the surface of the sensory cells that detect linear movement.
If free-floating otoconia find their way into the duct of an SCC (canalolithiasis) or attach themselves to the cupula of an SCC (cupulolithiasis), changes in head position in the plane of that SCC will result in displacement of the cupula, either directly in the case of cupulolithiasis or indirectly by altering endolymphatic fluid pressure in the case of canalolithiasis. The cupular displacement results in vertigo and nystagmus in the plane of the stimulated SCC. In cases where the otoconia are in the posterior or superior SCC, the nystagmus will be vertical-torsional i.e. rotary. In contrast, the nystagmus will be horizontal in cases where the otoconia are in the lateral SCC.
Below is shown a light micrograph of part of a human semicircular canal with the ampulla to the right of the image. Within the ampullae and running at right angle to the plane of this picture is the crista with the sensory hairs projecting from its surface.
Below is the crista of a seventeen year old showing the dense carpet of stereocilia
BENIGN PAROXYSMAL POSITIONAL VERTIGO
Benign Paroxysmal Positional Vertigo (BPPV) is a clinical diagnosis based on symptoms and physical signs.
BPPV is the onset of rotary vertigo as an individual adopts a particular position, commonly on lying down and turning to one side. The vertigo is severe, lasts for several minutes but then subsides to leave the patient feeling unsteady for a long while after. There are many variants and the feeling amongst ENT surgeons who deal with balance problems is that the condition in its non-classical form, is more prevalent than we thought.
The histo- pathology that has been suggested to account for this condition is that crystal deposits (otoconia) from the utricle make their way into the posterior semicircular canal (PSCC) and move about within the canal during certain head movements. This causes an erroneous signal which gives rise to the sense of rotary movement. The theory is slightly dubious and has not been confirmed although the response to treatment makes the suggested mechanism intuitively seductive.
BPPV may occur as a complication of head trauma or vestibular neuritis. Symptoms usually begin within days following the head trauma, whereas they may not begin for weeks or even years after an episode of vestibular neuritis. In some patients, BPPV occurs during the course of a progressive inner ear disease, such as Menière’s disease or Cogan’s syndrome. In most cases, however, no cause is identified.
The history is of vertigo – i.e. a sensation of unreal movement – that lasts for a while, not moments- and which may be associated with nausea. Its onset is associated with some turning movement but this may be obscured in the history. The general ENT and neurological examination is usually normal but the Hallpike test is often positive. In this test the patient is sat upon a couch with the doctor standing on one side. The patient’s head is held by the doctor and turned so that their eyes meet. The patient is then rapidly laid back so that their head is turned to one side, lying below couch level and their eyes are looking into the examiner’s eye. This is illustrated by diagrams a and b below.
In BPPV there is a short delay of up to 20 seconds, then the onset of marked vertigo with a rotary nystagmus [a rhythmic, oscillating, conjugal; movement of the eyes] which stops after a while i.e. it fatigues, and if the process is repeated then the severity is less i.e. it adapts.
Any other response is not BPPV and suggests central problems when an MRI scan is advised.
Specific therapies for the treatment of benign paroxysmal positional vertigo
In most cases the BPPV symptoms spontaneously abate within a few weeks, however, in up to 30 percent of untreated cases the symptoms may persist for months, resulting in significant disability and frustration for the patient. Although in the past BPPV was treated with vestibular habituation therapy specific mechanical therapies for the treatment of BPPV are now available. These include exercises and manoeuvres, based either on the cupulo- or canalolithiasis hypothesis. There is a growing body of evidence that these exercises and manoeuvres are highly effective in achieving symptomatic relief after a single or short-term application.
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Epley’s repositioning manoeuvre.
If the Hallpike test is positive – and when it is, it is usually quite clear- then the Epley manoeuvre is indicated. If the patient is able to perform the Hallpike test, then they are likely to be able to perform the Epley manoeuvre.
Epley developed the canalith repositioning procedure (CRP) based on the theory of canalolithiasis. The affected posterior-SCC is identified by the Hallpike manoeuvre and the latency and duration of nystagmus is noted in order to determine the timing of the procedure. The patient is sat on the table and brought down with the head turned by 45° to the affected side and extended over the edge of the table. The head is then turned 90° to the opposite side. This is followed by rotating the head and body 90° facing downwards (135° from the supine position), and the patient is next brought to the sitting position with the head turned 45° to the unaffected side. The CRP finishes with the patient in the sitting position and the head turned forward 20° Epley advocated repeating the manoeuvre until there is no nystagmus or no progress made in the last two cycles. He reported total resolution of symptoms in 90 percent, and resolution of BPPV but persistence of other symptoms in 10 percent of patients after the initial CRP treatment. There are several modifications of this manoeuvre involving longer maintenance at each position and gradual position changing with 30-second intervals.
The steps in the Epley manoeuvre are shown below.
The Epley particle repositioning manoeuvre for left posterior SCC-BPPV. The patient is rapidly reclined into the left Dix-Hallpike position (a) and remains in that position until both the vertigo and nystagmus have totally disappeared and the otoconial particles have settled into the lowest portion of the posterior SCC duct. The patient’s head is slowly turned by 90 degrees into the right Dix-Hallpike position (b-f), so that the particles are guided into the crus communis. Then the patient slowly rolls on to the right shoulder (g) and the head is turned another 90 degrees so that the particles fall via the crus communis back into the vestibule. The manoeuvre is completed by sitting the patient upright. Adapted from Halmagyi GM, Cremer PD. Assessment and treatment of dizziness. Journal of Neurology, Neurosurgery, and Psychiatry. 2000; 68: 129-36.
The Epley manoeuvre usually cures the patient if the diagnosis is BPPV but may require several treatments before resolution of the positional vertigo. Between treatments the patient may feel that the balance is not back to normal and there may be continued unsteadiness whilst the central balance mechanisms are compensating.
Brandt Daroff positional exercises
Brandt and Daroff proposed a mechanical self-treatment for p-BPPV, in the form of exercises that the patient should perform for 15 minutes three times daily. These exercises consist of a rapid sequence of lateral head/body tilts. Starting from the sitting position, the patient rapidly moves to the challenging position, i.e. lying on the affected side (nose 45° up) and remains in this position for at least 30 seconds or until the vertigo subsides. He/she then sits up for 30 seconds and then assumes the opposite head lateral and nose up position for 30 seconds before sitting up. The authors reported that 66 of 67 patients experienced complete relief from BPPV within 3–14 days in 98 percent of treated patients. However, a recent controlled trial showed resolution of BPPV in only 23 percent after one week.
Evidence for treatment efficacy
Numerous observational studies have shown response rates of approximately 50–70 percent after a single application of Epley’s procedure and approximately 80–90 percent after repeated trials. Both observational and randomized controlled trials show similarly good results for both Epley’s technique. However, a recent systematic review of the literature on the efficacy of the Epley manoeuvre in treating p-BPPV only identified two randomized controlled trials that fulfilled stringent criteria, which compared the Epley manoeuvre with a sham manoeuvre. Hilton and Pinderconcluded that while there is some evidence that this manoeuvre is a safe and effective treatment for p-BPPV, there is no definitive comparative study on the relative merits of CRP versus other physical, medical or surgical therapy.
Tony Wright.
Spring 2025.
