Can hyperventilation test and duration of spontaneous nystagmus help differentiate between vascular and inflammatory aetiology of acute unilateral vestibular deficit?

Objective: To relate clinically the duration of spontaneous nystagmus and hyperventilation-induced nystagmus (HVIN) to vascular or inflammatory aetiology of acute unilateral vestibulopathy observed in a very early stage. Methods: This is a retrospective study on 198 patients with acute unilateral vestibulopathy. Results: In the short-lasting nystagmus group (spontaneous nystagmus < 48 h), mean age and cardiovascular risk were significantly higher; the rates of negative HVIN and paretic HVIN were 41.7% and 58.3%, respectively. In the long-lasting nystagmus group (spontaneous nystagmus > 48 h), mean age and vascular risk were lower; HVIN was absent in 12.6% of the cases, HVIN excitatory patterns were observed in 40.3% of cases and a paretic pattern in 47.1%. Conclusions: A vascular aetiology should be considered the most likely in patients with spontaneous nystagmus < 48 hours: all patients were > 60 years old, cardiovascular risk was higher and HVIN was always absent or paretic. In the group with nystagmus > 48 hours, similarly, data indicate a higher incidence of paretic HVIN in older patients and higher vascular risk, even if the data does not allow us to lean clearly towards one of the two aetiological hypotheses.

Less common forms of posterior canal benign paroxysmal positional vertigo.

The most common form of posterior canal benign paroxysmal positional vertigo (BPPV) is characterised by positional, paroxysmal, upbeat nystagmus, with a torsional component beating towards the downward ear. Rarer variants have been reported, putatively due to either the position of otoconia in the canal or anatomic variations of the semicircular canals. The most frequent less common form is apogeotropic posterior canal BPPV, in which the positional nystagmus is downbeat and torsional apogeotropic. In this form, the main problems are differential diagnosis with central mimics of BPPV and identification of the affected canal and its side. The authors propose a new subtype of apogeotropic posterior canal BPPV hypothesising the localization of otoconia in the ampullary tract of the affected canal, which might explain the modality of the conversion in typical posterior canal BPPV which they observed in some of these cases. If nystagmus of the less common forms of posterior canal BPPV is explicable through purely peripheral mechanisms, these forms should no longer be defined as "atypical" but, in a less demanding way, as "less common" variants, which must be recognised by any expert otoneurologist.^ieng

La forma più comune di vertigine parossistica posizionale benigna (VPPB) del canale posteriore è caratterizzata da nistagmo posizionale, parossistico, verticale in alto, con componente torsionale verso l'orecchio posizionato più in basso. Varianti meno comuni sono presumibilmente dovute alla posizione degli otoliti nel canale o a variazioni anatomiche dei canali semicircolari. La forma rara più frequente è quella apogeotropa, in cui il nistagmo posizionale batte verso il basso e la componente torsionale batte in opposizione all'orecchio malato. In questa forma, i problemi principali sono la diagnosi differenziale con le forme centrali di vertigine posizionale e l'identificazione del canale e lato interessati.Gli autori propongono un nuovo sottotipo di VPPB apogeotropa del canale posteriore, ipotizzando la localizzazione degli otoconi nel tratto ampollare del canale interessato, il che potrebbe spiegare la modalità della conversione in forma tipica del canale posteriore osservata in alcuni di questi casi. Se il nistagmo delle forme meno comuni di VPPB del canale posteriore è spiegabile attraverso meccanismi periferici, queste forme non dovrebbero più essere definite come "atipiche" ma, in modo meno impegnativo, come varianti "meno comuni" la cui conoscenza è richiesta all'Otoneurologo esperto.

The Video Head Impulse Test in the acute stage of posterior canal benign paroxysmal positional vertigo.

OBJECTIVE: Study the high-frequency vestibulo-oculomotor reflex in posterior canal benign paroxysmal positional vertigo (BPPV) through Video Head Impulse Test (vHIT). METHODS: 150 patients suffering for the first time from posterior canal BPPV were studied. Posterior canal vestibulo ocular reflex (VOR) gain was analysed through stimulations in right anterior-left posterior and left anterior-right posterior planes before treatment, immediately after resolution of the acute stage and one month later. Results were compared with a group of 100 healthy individuals. RESULTS: No significant difference between the study the control groups was observed, except for normalised asymmetry ratio of the posterior canal which was significantly higher in the study group. VOR gains of both affected posterior canals and contralateral healthy posterior canals were not significantly correlated with the VOR gain of ipsilateral and contralateral anterior canals. CONCLUSIONS: vHIT does not seem to represent an essential tool to study typical posterior canal BPPV in patients affected by this disease for the first time. Different results might be expected in relapsing forms, non-responsive forms, long lasting forms, or atypical variants in which major damage could be provoked by the persistence of otoconia in the canal or by its complete or partial jam.