The following articles will give a reasoned interpretation of the various maneuvers that will gradually be described in the most elementary way possible, commenting step by step what happens inside the semicircular canals during the execution of the maneuvers itself.
We have already diagnosed a benign positional paroxysmal vertigo of the lateral canal. Liberating maneuvers have the purpose to determine and facilitate the sliding of the mobile otoconial mass, inside the lateral canal, towards the utricle.
The maneuvers proposed are all valid, and the choice to perform one rather than the other is often taken by the clinician due to different and contingent factors, and in particular: the diagnostic maneuver adopted, the position reached by the patient at the time of diagnosis, and the operator’s experience and preferences.
Let us briefly remind the pathophysiology of the lateral canal BPPV.
- The otoconia detached from the utricular macula become slide inside the lateral semicircular canal (LSC).
- The patient reaching particular positions (decubitus) o performing particular movements of the head, determine the movement of the otoconial mass which, because its volume, induces an endolymphatic current that can be ampullifugal (away from the ampulla) or ampullipetal (toward the ampulla), in relation to the position of the otoconial mass inside the LCS.
- In LCS the ampullipetal endolymphatic current is excitatory in LCS, while the ampullifugal current is inhibitory.
- The LSC is functionally connected to the brainstem’s oculomotor nucleus of the III and VI and, through them, with the extrinsic eyes muscles: stimulation of a CSL will determine:
- The contraction of the ipsilateral rectus medialis muscle and contralateral rectus lateralis muscle.
- The relaxation of the ipsilateral rectus lateralis muscle and contralateral rectus medialis muscle.
The clinical examination shows a pure horizontal nistagmus, with no torsional or vertical components, as it is generated exclusively by the ampullar receptor of the LSC. It is paroxysmal, geotropic or apogeotropic, slightly inhibited by fixation, fatiguing, exhaustible.
In the Geotropic variety otoconial mass is placed in the non-ampullary arm of the LSC and therefore near the access in the utricle.
In the Apogeotropic variety the otoconial mass is placed in the ampullary arm of the LSC and therefore far from the canal access in the utricle (Short arm of the semicircular duct), so it is necessary, before performing the liberating maneuver properly said, to perform a propaedeutic maneuver, called repositioning maneuver, that moves the otoconial mass into long canal’s arm.
The successful transformation of the Apogeotropic form into a geotropic form can be easily documented by observing the direction of the Nistagmus induced by the Pagnini-MClure maneuver.
We will describe Gufoni’s maneuver.
The maneuver is simple to perform and very efficient. The correct diagnosis will lead us to the correct choice of the proposed variety of maneuvers and then to the resolution of the symptomatology.
The required instrumentation is extremely simple but necessary: a visual fixation suppression system in order to be able to read with extreme precision the quality of the observed nystagmus.
The maneuver provides four successive positions and it is differently performed about the fact that we are treating a geotropic form or an apogeotropic form.
BPPV geotropic form ( Otoconial debris in the long arm of the semicircular duct)
Once identified the involved side, we proceed with the liberatory maneuver. In the following pictures, it is illustrated an hypotetical canalolithiasis of the non-ampullary arm of the left LSC.
The patient, sitting with his legs hanging out the bed, is quickly tilted on the healthy side until he arrives with his head on the table;
This positioning maneuver generates geotropic nystagmus which tends after a few minutes to disappear completely, sometimes it can persist for longer but anyway a progressive reduction of the angular slow-phase velocity (ASPV) will be observed.
The patient’s head is then rotated abruptly about 90 ° down towards the table:
This rotation can generate:
- the appearance of nystagmus having the same direction of the nystagmus observed in the previous positioning and disappeared during the maintenance of the position itself;
- the increase of angular slow-phase velocity (ASPV) of the nystagmus that had not been exhausted during the previous positioning.
In both cases, the observed nystagmus is the proof of the gliding of the otoconial mass towards the utricle.
On the other hand, if during the second step we don’t observe any nystagmus, it means that we have not induced any movement of the otoconial debris and therefore this indicates that the maneuver we are performing is not efficient.
The patient is returned to a sitting position with a rapid movement.
The manoeuvre is repeated three times, and if it is effective, at each manoeuvre the nystagmus size is progressively reduced until it disappears.
BPPV in the apogeotropic form: otoconial mass in the ampullary (short) arm.
Once identified the involved side, we proceed to a preliminary time with the transformation’s maneuver from the apogeotropic to the geotropic form.
The patient, sitting with his legs hanging out the bed, is quickly tilted on the involved side until he arrives with the head on the table;
this position generates an apogeotropic nystagmus which tends, after a few minutes, to disappear completely, sometimes it can persist for longer but anyway a progressive reduction of angular slow-phase velocity (ASPV) will be observed.
The patient’s head is then rotated abruptly about 90°up, upwards.
If the transformation manoeuvre is really efficient, we will observe, the reappearance of the nystagmus (Apogeotropic) previously observed or the increase of the angular slow-phase velocity (AVSP) if the nystagmus previously observed was not completely exhausted.
However, the observation of the nystagmus described in the second step indicates the sliding of the otoconial debris towards the non-ampullary arm.
The patient is returned to a sitting position with a rapid movement.
The manoeuvre is repeated three times, and if it is efficient, at each maneuver the nystagmus intensity reduces progressively until it disappears.
Then it is performed the Pagnini-McClure manoeuvre to confirm the transformation from the apogeotropic form into the geotropic one.
Now it is possible to perform the liberating manoeuvre above described.
The unsuccessful transformation from the apogeotropic into the geotropic form is generally due to otoconial debris adhered to the ampullary cupula, or when there is a narrow tract in the semicircular canal. Thus the otoconial mass founding an obstacle stops its sliding towards the utricle and comes back.
In this case, we advise not to insist too much with the maneuver, because it generates only vertigo not functional to the pathology’s resolution and to advise patients to perform the “forced decubitus” ( Vannucchi).