BPPV of the Posterior Semicircular Canal (PSC)
A condition presenting short-lasting rotational dizziness bursts due to position as they are associated with certain head movements. The typical patient is someone who wakes up in the morning or in the middle of the night with the onset of dizziness, which can also happen upon getting up or turning over during night sleep.
The onset is sudden and abrupt and often lasts less than a minute, with its disappearance when a different head position is assumed. It is defined as paroxysmal due to the parallel trend between symptoms and nystagmus observed in videoculonystagmoscopy. In fact, nystagmus and vertiginous symptoms increase as the provoking position is assumed, reaching an apex which lasts for a few seconds and then rapidly decreases. Nystagmus is generally evoked through the Semont diagnostic and Dix-Hallpike positioning manoeuvres.
In the DIX HALLPIKE POSITIONING MANEUVER, the patient is initially sitting on the examination table. The head is then rotated 45° to one side after which the patient is brought down into supine position with the head extended over the end of the table. If the side examined is the one affected by PSC lithiasis, after a latency that can range from a few to 15-20 seconds, the typical nystagmus of the condition appears. Upon the patient returning to a sitting position, reversal of previous nystagmus might occur.
The SEMONT DIAGNOSTIC MANEUVER requires the patient on the table to be moved to one side with the head rotated by about 45° counter laterally.
The BPPV of the PSC is present in two nystagmus forms, namely the GEOTROPIC FORM and the APOGEOTROPIC FORM.
In the Apogeotropic Form, the nystagmus is induced by any movement on the planes of both PSCs, has a much lower intensity and its paroxysm is less evident, unlike the Geotropic Form in which the nystagmus is triggered by the positioning on the pathological side with much more evident paroxysm.
Nystagmus, which should always be observed in videoculonystagmoscopy, in the GEOTROPIC FORM occurs as:
- DISSOCATED because the two phases, Rapid and Slow, beat in different directions in the two eyes, that is, predominantly rotatory in the pathological side and predominantly vertical in the other.
- GEOTROPIC, that is, beating in the gravitational direction of positions inducing nystagmus
- BRIEF DURATION, generally one minute at most
- PAROXYSTIC as it rapidly increases to an apex or plateau which is maintained for a variable time until it slowly decreases and disappears.
- REVERSE to seated repositioning of the patient, where it can appear as downbeat nystagmus
- EXTINGUISHABLE through repetition of the provoking positions
In the APOGEOTROPIC FORM the following characteristics of nystagmus can be described
DISSOCATED as rotational in the affected side and vertical in the other, with clockwise torsion in rapid phase in the right PSC and counterclockwise in the left PSC, and predominantly vertical linear phase in both eyes.
MAINLY APOGEOTROPIC due to its down beating characteristics
EXTENDED DURATION until it seems inextinguishable
PAROXYSIMAL also considering the slow reduction of the intensity
ABSENCE OF REVERSAL upon resumption of sitting position, and likely prolongation of down beating
REDUCED EXTINGUISHABILITY, sometimes absent, especially with the repetition of positioning, with dizzying symptoms that are much less intense than in the geotropic form, but higher presence of instability / dizziness
In the BPPV of the PSC the main liberating manoeuvres are EPLEY and SEMONT.
Therapeutic manoeuvre aimed at the mechanical release of the PSC from otolithic debris.
The patient is seated on the table with legs dangling and brought into the Dix-Hallpike position by rotating the head towards the side evoking the vertigo, holding the position for a duration varying between 2 and just over 3 minutes, that is, the time of the duration of the nystagmus, which in turn corresponds to the sliding of debris along the canal. At the end of this phase, the patient is rotated slowly but continuously towards the unaffected side. The rotation should cause the patient to rotate to the point where the head is facing the floor. This position is held for another 2-3 minutes and then the patient is returned to a sitting position. Once assuming the position with the head turned towards the unaffected side, or when the patient is seated, if nystagmus appears with the same characteristics as that which arose when positioned on the pathological side, it is an indication of the good result obtained from the manoeuvre.
The patient is seated on the table with legs dangling. The head is rotated about 45° towards the unaffected side, and the trunk moved on the pathological side, basically assuming a supine position. Upon nystagmus appearance, the position must be held for at least one minute. After that, without changing the angular rotation of the head, in a quick and above all uninterrupted manner, the patient is brought onto the other side. The appearance of nystagmus in this position indicates the success of the manoeuvre. The patient holds this position for at least one minute, to be brought back to a sitting position, always without changing the rotated position of the head.