(vv)Strupp.mp4(tt)
From: Struppp M. Clinical Examination of the Ocular Motor and Cerebellar Ocular Motor System. From: https://www.youtube.com/watch?v=meXAjVoQdCI
Peripheral nystagmus arises from an acute lesion of the peripheral vestibular system, which includes the labyrinth, vestibular ganglion, and vestibular nerve. However, acute lesions of the lateral medulla, lateral pons, or inferior cerebellum lesions may mimic acute unilateral vestibulopathy and the expected brainstem features such as ataxia or dysarthria may not be present.
It is important to be cautious of linking a relatively non-specific symptom, such as vertigo, with a specific underlying cause such as a presumptive disorder of the vestibular system, and also to be cautious of attributing symptoms of posterior circulation ischaemia/infarction to the peripheral vestibular system :
- Recurrent episodes of dizziness lasting seconds to minutes over the preceding weeks or months may indicate underlying cerebrovascular disease, rather than a vestibular cause. Prodromal, isolated attacks of vertigo are well described in vertebrobasilar stroke1. Vertigo is the commonest symptom suggestive of nervous system involvement in patients with vertebral dissection.
- Virtually all patients with an acute vestibular syndrome report exacerbation of symptoms with head movement, and this does not distinguish between lesions of the peripheral vestibular nerve and the brainstem/cerebellum.
-It is likely that disproportionate symptoms (neurovegetative (nausea, vomiting); gait/postural symptoms) are more commonly found with stroke than peripheral vestibulopathy.
-Drop attacks and room tilt illusions are likely pointers to brainstem ischaemia. - It is an error to assume that hearing loss automatically indicates a benign peripheral cause in the presentation of an acute vestibular syndrome: hearing loss may arise from ischaemia of the labyrinth or cochlea. Dizziness, hearing loss and tinnitus may occur due to posterior circulation stroke or TIA, and it is similarly unwise to diagnose acute Menière’s disease, when posterior circulation ischaemia is a possibility.
- The expectation that there will be clear-cut brainstem signs is not supported by available evidence. Fewer than half of patients with acute vestibulopathy due to a central cause had clear neurological signs suggesting brainstem involvement2. The general neurological examination therefore has relatively low sensitivity for detecting features of an acute vestibular syndrome1 of brainstem origin. Diplopia (which is rare in vestibular migraine) needs to be distinguished from oscillopsia, which is present in the majority of patients with vertigo.
The vascular territories most often involved are:
- The posterior inferior cerebellar artery (PICA) which supplies the important structures of the inferior cerebellar peduncle, medial vestibular nucleus (MVN), and, in particular, the nodulus. This may also cause an incomplete ocular tilt reaction.
- The anterior inferior cerebellar artery (AICA) which sometimes causes an abnormal head impulse VOR either by involvement of the flocculus or, in some cases, through labyrinthine infarction. It is most often associated with unilateral hearing loss (due to cochlear ischemia) or additional brainstem signs.
- Less commonly, lesions in the superior cerebellar artery territory may also be affected.
The MVN in the medulla receives inputs from the cristae of the semicircular canals, the maculae of the otoliths, the visual (optokinetic) system, and from proprioceptors in the neck. Consequently, a demyelinating lesion in the root entry zone or in the MVN can produce a central lesion with features of a peripheral vestibular syndrome (sometimes called a vestibular pseudoneuritis).
However, there are reliable methods to distinguish an acute vestibulopathy of peripheral origin from a brainstem lesion3:
- Use Frenzel lenses to detect peripheral vestibular spontaneous nystagmus, which will suppress with visual fixation, and become more apparent with the use of Frenzel lenses.In the very acute phase patients may only partially suppress their spontaneous nystagmus with visual fixation.Note also that there are central causes of nystagmus which may also be suppressed by visual fixation."Nystagmus which can not be reduced by visual fixation is not peripheral,".
- Examine smooth pursuit, which, if saccadic, is likely to point to a central lesion.
- Examine for disturbance of the Subjective Visual Vertical (SVV).
Use the HINTS exam: Head-Impulse, Nystagmus, Test of Skew2 (HINTS plus includes acute hearing loss)
- Head Impulse Test: if normal, suggests a central lesion. That is, the counter-intuitive finding is that a normal head-impulse test is of greater concern than an abnormal test.
- Nystagmus. Peripheral vestibular nystagmus is a horizontal spontaneous nystagmus with a rotational component3.
If the direction of nystagmus changes, this would suggest the presence of gaze-evoked nystagmus, due to involvement of the brainstem-cerebellar neural integrator. Specifically, gaze evoked nystagmus towards the affected ear would suggest a central lesion (‘‘gaze evoked’’ nystagmus towards the unaffected ear can simply be caused by spontaneous vestibular nystagmus). - Use the alternating cover test to look for skew deviation, which if present, is likely to point to a central lesion. With a patient fixating on a small central target like the tip of a pen, the normal response to alternately occluding each eye (alternate cover test) is for the eyes to remain motionless, because the eyes normally have little or no propensity toward misalignment (particularly vertically).
The rare occurence of a clinically evident skew deviation in a peripheral lesion is more common in patients with complete peripheral deafferentation affecting the superior and inferior vestibular nerves, as occurs with iatrogenic lesions (vestibular neurectomy or labyrinthectomy) or sometimes in herpes zoster oticus4).
The dangerous signs can be remembered using the acronym : I.N.F.A.R.C.T. (Impulse Normal, Fast-phase Alternating, Refixation on Cover Test).
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1. Head Impulse Test:
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Normal HIT |
Normal HIT |
(However, a positive HIT can result from either a peripheral or central site2, since |
2. Nystagmus
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Opposite direction to
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The nystagmus typical of a central cause may be distinguished from a peripheral lesion by there being a change in direction on eccentric gaze in cases due to a central lesion; this would sugggest an AICA infarction. The test has high specificity but low sensitivity1. |
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3. Test of Skew |
Skew deviation with
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Saccadic Pursuit |
Saccadic pursuit indicative of central cause, especially vertically. |
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Acute moderate to severe sensorineural hearing loss associated with tinnitus and/or vertigo may be the result of labyrinthine infarction. (AICA supplies the cochlea via the labyrinthine artery, which also supplies the vestibular apparatus). |
(vv)Vertigo Maneuvers Performing The Hints Exam.mp4(tt)
(vv)Big 3 Of Vertigo.mp4(tt)
Right beating nystagmus on looking to the right; HIT is normal.
Removal of fixation showed a unidirectional, primary gaze, right-beating nystagmus that increased in right gaze, compatible with a peripheral-type nystagmus
Saccadic pursuit to the right, and normal pursuit to the left.
(vv)Kattah_Video1b_Picastroke_Hitnormal.mp4(tt)
Probable vestibular migraine. Left-beating nystagmus that stayed left-beating in all directions of gaze, more so in left gaze (in accordance with Alexander's Law), and less in right gaze. This pattern is more commonly seen with peripheral, rather than central disturbances.
(vv)Unidirectional vestibular nystagmus.mp4(tt)
From: Gold D. Unidirectional vestibular nystagmus. Video. [Neuro-Ophthalmology Virtual Education Library: NOVEL Web Site]. 2018.
Available at: https://collections.lib.utah.edu/details?id=187732
Central lesions of the vestibular system often affect the gaze holding circuits; in this case the nystagmus may reverse direction when the patient looks in the direction of the slow phase. The video shows left beating nystagmus in primary gaze, increasing in amplitude on looking to the left (in accordance with Alexander's law) and gaze evoked nystagmus on looking to the right, due to damage to gaze holding circuits. Patient had a cerebellar infarction.
(vv)Katta Central_Lesion_With_Direction_Changing_Nystagmus.mp4(tt)
From: Newman-Toker D.Central Lesion with Direction-Changing Nystagmus. Video. [Neuro-Ophthalmology Virtual Education Library: NOVEL Web Site]. 2009.
Available at: https://collections.lib.utah.edu/ark:/87278/s6vm4dwm
(vv)TestSkew.mp4(tt)
(vv)Altcover1.mp4(tt)
From: Struppp M. Clinical Examination of the Ocular Motor and Cerebellar Ocular Motor System. From: https://www.youtube.com/watch?v=meXAjVoQdCI
Patient has an obvious vertical ocular misalignment: a skew deviation.
The right eye is hypotropic (refixation saccade upward), whereas the left eye is hypertropic (refixation saccade downward), consistent with the right lateral medullary location of the stroke.
(vv)Kattah_Video3_Latmedullastroke_Skewaltcover.mp4(tt)
From: http://stroke.ahajournals.org/content/vol0/issue2009/images/data/STROKEAHA.109.551234/DC1/Kattah_Video3_LatMedullaStroke_SkewAltCover.wmv
Nystagmus was left-beating with a torsional component (top poles beating toward left ear), the left-beating nystagmus lessened in right gaze, and continued to beat to the left with vertical gaze, and increased in left gaze (in accordance with Alexander's law).
The HIT was abnormal to the right side, and nystagmus also increased in intensity with removal of fixation. This finding, combined with his unidirectional, mixed horizontal-torsional nystagmus, are typical findings of a peripheral vestibular lesion(but rarely may be seen with a central disorder). Rightward horizontal gaze deviation was noted on the MRI, but this does not indicate a central lesion.
However, a right hypotropia was apparent in primary gaze with cover-uncover testing, which was consistent with a skew deviation.
A week later the right hypotropia persisted, and was present in all directions of gaze, and fundus photographs showed a small degree of ocular counterroll towards the right ear, suggesting an ocular tilt reaction, although there was no head tilt.
Video HIT demonstrated abnormalities in the planes of the right horizontal and anterior canals, both of which are innervated by the superior division of the vestibular nerve, suggestive of an acute vestibulopathy. Repeat MRI scan was normal, and specifically, no brainstem or cerebellar lesion was present.
(vv)vestOTR.mp4(tt)
From: Gold D. Vestibular neuritis with a peripheral skew deviation. Video. [Neuro-Ophthalmology Virtual Education Library: NOVEL Web Site]. 2018.
Available at: https://collections.lib.utah.edu/ark:/87278/s6ht70fx
(vv)Big5saccadicSP.mp4(tt)
From: Struppp M. Clinical Examination of the Ocular Motor and Cerebellar Ocular Motor System. From: https://www.youtube.com/watch?v=meXAjVoQdCI