Comment

When assessing a patient with vertigo, it is the timing and triggers of symptoms rather than just their nature that helps distinguish between different vestibular syndromes, and each has a specific treatment strategy.1 2

There are two common diagnostic scenarios: an acute vestibular syndrome, with prolonged dizziness or vertigo over 24 hours, nausea, vomiting and balance issues, and an episodic vestibular syndrome, manifesting spontaneously or triggered by movement.3

It is essential to identify whether an acute vestibular syndrome has a central (potentially sinister) or peripheral origin (more common and less urgent). Vestibular neuritis is a common cause of a peripheral acute vestibular syndrome and is characterised by spontaneous onset of symptoms,2 unlike this patient’s symptoms where vertigo was seemingly provoked by head movement.

Additionally, she had acute, transient symptoms including left-sided facial weakness, sensory loss in the right arm and slurred speech, raising the possibility of a posterior circulation transient ischaemic attack (TIA).

A transient ischaemic lesion involving the lateral portion of the caudal pons, including the short and long vertebrobasilar branches, could explain left-sided facial weakness (facial nerve), sensory loss in the right arm (spinothalamic tract) and slurred speech (corticobulbar pathways).

Additionally, transient occlusion of the left posterior inferior cerebellar artery branches at the level of the lateral medulla could explain vertigo, nausea, vomiting and nystagmus caused by damage to the vestibular nuclei as well as sensory loss in the right arm due to spinothalamic tract involvement.

The ataxia could result from damage to the middle cerebellar peduncle or other cerebellar structures at the lateral caudal pons or inferior cerebellar peduncle when involving the lateral medulla. The patient’s vascular risk factors and the rapid emergence and resolution of symptoms support a transient ischaemic event.

Nevertheless, the persistence of her vertigo, with her other symptoms resolving, means that a TIA does not entirely account for her presentation.

The predominant symptoms of intense rotational vertigo and nausea that resolved when she is stationary but worsened with head movement suggest that an episodic vestibular syndrome is the most likely, commonly caused by benign paroxysmal positional vertigo (BPPV). The correlation of short-duration vertigo with head position changes suggests that BPPV yet does not account for her other neurological symptoms.3

Other possible causes include postural hypotension, although this usually causes orthostatic dizziness, which she did not have. Vestibular migraine symptoms are increasingly recognised to overlap with those of BPPV. Thus, despite not meeting the strict criteria to diagnose vestibular migraine (having not had previous similar episodes), her preceding headache episodes and a background of motion sensitivity made vestibular migraine plausible.

Although vestibular migraine usually causes spontaneous dizzy episodes, patients frequently say their vestibular symptoms are triggered by (and aggravated by) head motion or changing head positions, such as supine or side-lying, as in this patient.4 5 Interestingly, BPPV is well known to act as a migraine trigger,6 complicating the diagnosis in patients with positional vertigo where the two conditions can coexist.

Comment

The pathophysiology of nystagmus in BPPV relates primarily to the canalolithiasis hypothesis, which suggests that the cause is the dislodgement of otoconia within the semicircular canals.3 7 Diagnostic manoeuvres such as the Dix-Hallpike and the supine roll test (McClure-Pagnini test) often allow differentiation between central and peripheral causes of vertigo by examining nystagmus characteristics.8 9 BPPV-associated nystagmus has a crescendo–decrescendo pattern and varies in direction with gaze.10 This nystagmus gradually intensifies over a few seconds and fades within 60 s.10

This patient’s persistent horizontal vertigo, present only with head position changes, was most consistent with a lateral canal BPPV. The Dix-Hallpike test induced horizontal nystagmus, while the supine roll test induced intense geotropic nystagmus, more pronounced on the left side, indicating a peripheral vestibular disorder.8 10 The patient’s inability to stand without support suggested a potential central cause, underscored by significant truncal ataxia.11

Central positional nystagmus is linked to structural abnormalities in brain regions such as the cerebellar vermis and brainstem, affecting vestibular signal integration,2 but can also occur without imaging findings. Central positional nystagmus often mimics BPPV but can be identified by distinct nystagmus patterns and underlying cerebro-vestibular involvement.2 12

Comment

Although MR imaging has low sensitivity in this scenario, this should be considered.1 This patient had an MR scan of brain performed 8 hours after symptom onset, showing no ischaemic lesions. A fat-saturation MR cervical angiogram excluded an arterial dissection. Repeat MR scan of brain after 48 hours remained unremarkable, effectively excluding a stroke but not a TIA.

Videonystagmography is used to evaluate vestibular disorders and particularly helps the diagnosis of episodic vestibular syndrome. In this patient, the nystagmus had a very short latency following provocation manoeuvres, suggestive of central positional nystagmus (figure 1). Moreover, oculography showed a subtle torsional component in addition to bilateral geotropic nystagmus during roll-test manoeuvres, which also raised the suspicion of a central cause. Finally, the patient vomited following positioning manoeuvres, which is another diagnostic clue favouring central positional nystagmus.2

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Figure 1

Schematic representation of the Dix-Hallpike manoeuvre with anatomical icons (without colour) where we can see the otoconia represented in red, with its movement after the manoeuvre represented by a curved arrow. The excitatory pathways influence compensatory eye movements.10 Each semicircular canal directly influences a pair of extraocular muscles, which move the eyes approximately in the plane of the respective canal, irrespective of the initial position of the eye in the orbit.10 Stimulation of a single canal elicits slow-phase eye movements in a plane parallel to that of the stimulated canal.10 The figure highlights how (1) identifying central neurological features in a patient with acute vertigo is the first step to making a diagnosis, and (2) carrying out a Dix-Hallpike manoeuvre can not only help to confirm benign paroxysmal positional vertigo as a cause of vertigo (green) but also identify central neurological signs that support a central cause (blue).

On discharge, the potential diagnoses included a posterior circulation TIA and a first episode of vestibular migraine, with or without left lateral canal BPPV. However, we considered lateral canal BPPV to be a likely and treatable diagnosis, supported by a positive response to the barbecue manoeuvre to the right. During follow-up, the patient had five more episodes of positional vertigo with similar nystagmus characteristics but no other neurological deficits, and the positional treatment manoeuvres did not alleviate these episodes.

Given the patient’s age and ongoing symptoms of nausea and vertigo that did not improve with repositioning manoeuvres, along with atypical signs, we considered other non-structural causes of central positional nystagmus. These included less common but potentially treatable causes such as autoimmune paraneoplastic syndromes. Consequently, we arranged a lumbar puncture and full-body positron emission tomography-MRI, both of which were normal.

Considering the lack of positive results from these investigations, coupled with the ongoing symptoms despite treatment efforts and the nature of the episodes, vestibular migraine (non-structural central positional nystagmus) seemed the most plausible explanation. The timing of the initial response to repositioning manoeuvres had probably aligned with the phase of acute migraine resolution. At follow-up, an experienced vestibular neurologist (DK) made a working diagnosis of vestibular migraine and prescribed a nightly dose of amitriptyline 10 mg as a preventive measure, with gradual symptom improvement over 3 months.

Vestibular migraine has a very variable semiology as it can present with rotational vertigo, increased motion sensitivity and intolerance to visual stimuli but also with position-dependent dizziness, as here.3 Symptom duration varies substantially; some patients’ symptoms last only for seconds, while others have persistent vertigo; only 20% are in the clinical range of a migraine aura (5–60 min).3 Furthermore, the association between vertigo and headaches is variable, with some studies showing that only 70% of cases have these present at the same time.3 Vestibular migraine is the second most frequent cause of episodic vertigo/dizziness after BPPV but may be more common than BPPV in younger people. Women are affected five times more often, and vertigo attacks are often delayed by years or decades after the onset of migraine headache. Additionally, some studies have shown that vestibular migraine increases at the onset of menopause, whereas migraine headaches may become less frequent.3

From a pathophysiological standpoint, hypersensitivity within the nodulus and uvula probably suppresses the vestibular nuclei interictally, while during attacks, excitation from migraine-associated brainstem regions overcomes this suppression, leading to positional nystagmus and vertigo.3 4 This could explain the transient neurological symptoms previously attributed to a TIA in this patient.4

This case highlights how vestibular migraine sits at the crossroads of neurology and otology, representing a commonly overlooked cause of central positional nystagmus. Despite its widespread occurrence, healthcare providers do not often diagnose vestibular migraine, given its intricate symptoms and nuanced presentation.