PARADOXAL MUSCLE TONE IN PATIENTS WITH BENIGN PAROXYSMAL POSITIONAL VERTIGO

by
Sixten Albertus MD
Head of Department
Ear Clinic, Karlskoga Hospital, Sweden 1998

Benign Paroxysmal Positional Vertigo, BPPV, was first described by Barany 1921. In 1952 Dix & Hallpike developed the provocative test that has become known as Hallpikes maneuver. The maneuver implies that the patient is transferred from sitting position to one where the head is hanging down at the same time as it is turned to one side. A positive result is obtained when there is a rotational eye movement with, in accordance with the classical, the rapid nystagmus in geotropic direction. Nystagmus is seen after a few seconds of latency, has a duration of usually between 5 and 15 seconds , less than 60 seconds, and becomes extinguished upon renewed provocation.

In 1962 Schknecht presented a theory on the causality, known as cupulolithiasis theory, or the hevy cupula theory.

In 1993, Yohi Zennou-Azogui et al. published a report on cats subjected to an unilateral vestibular neurectomi. The spontaneus neck muscle EMG activity in M. splenius capitis was then registered bilaterally. During the acute phase, the cats showed a severe lack of balance in the spontaneus neck muscle activity, characterised by increased muscle tone in the ipsilateral splenius capitis muscle and hypoactivity in the contra-lateral, non-operated side. EMG activity did not return to normal until after 5-6 weeks.

As BPPV often behaves in periods and rather sporadic, there was an idea that a demand to some sort of disinformation of central vestibular organizing centre, alternative disturbance of an alredy established compensation against patological endolymphatic movements in the posterior canal could exist, in order that the canalpathology should be able to start an attack of vertigo. In the search for such a disinformation the attention was called to the function of the neck muscles and specially to the muscles of Sterno-Cleido-Mastoideus, since Hallpikes maneuver involve a factor of headtorsion.

Material and methods
In connection with the ongoing outpatient care program all patients suffering from vertigo were subjected to EMG studies of the S-C-M musculature on both sides with surface electrodes glued to the skin. The active electrode was placed over the main portion of the muscle,while the indifferent electrodes were taped centrally to the neck above the spinous processes.

55 consecutive patients suffering from positional vertigo were studied in this way. Among these, Hallpikes maneuver gave results that enabled BPPV to be diagnosed in 40 cases. Among the 15 remaining patients, the diagnosis could only be reached anamnestically. Diagnostic criteria were severe vertigo in connection with lying down and turning the head to one side, and/or that the attacs of vertigo were the result of turning the head or body when supine, usuly while asleep. Several patients had experienced an attack of that kind during the previous week.

The patients with positionel vertigo aged between 28 and 81 years, with a mean age of 61. The controls consisted of 59 persons who suffered from various kinds of vertigo, but did not have a medical history of positional vertigo. Their age varied between 19 and 85 years, with a mean of 58 years.

On patients with BPPV, the EMG study was always carried out at the first visit to the clinic, together with Hallpikes maneuver. Electronystagmography could rarely be done until a week later.

During the EMG study, the patient was allowed to sit and the procedure followed a precribed plan. The patient was asked to bend his/her head effective but not extreme 1) stright forward 2) stright backward 3) to the left and forward 4) to the left and backward 5) to the right and fotward 6) to the right and backward. Each position has been statically maintained for about 20 seconds. The movements were active without any support.

Results
When turning the face to one side, it is normally the contralateral S-C-M-musculature that is activated, while the ipsilateral muscle should be relaxed. However, in many cases, there was also hyperactivity in the ipsilateral muscle. We have chosen to call this reaction "paradoxical".

Among the 40 patients with BPPV, 36 showed a paradoxal muscle reaction when in sitting position, they turned their heads backward with the face towards the Hallpike positive side. 10 of them showed paradoxical reaction also when turning to the negative side. In 4 cases, Hallpikes maneuver was positive when turning in both directions, and in those cases we also observed a bilateral paradoxical reaction. In 3 cases, no paradox was found on either side.

Among the controls with no medical history of positionel vertigo, there were paradoxical muscular reactions in relation to head movements in 13 of the 59 persons..
Among the 55 patients with positionel vertigo, 28 complained of pain in the neck, from witch 24 at the positive side. Nystagmografi was normal in 50/55 patients.

Discussion
The study shows a connection between paradoxical muscular reactions, neckpain and Benign paroxysmal positional vertigo

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