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VNG (Videonystagmography) Report - Interpretation

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Test-by-Test Analysis

1. Saccades (Eye Movement Accuracy)

• Horizontal saccade velocities and latencies are broadly within acceptable limits for age 77.
• Vertical saccades at 0.45 Hz show markedly prolonged latencies (491 ms / 457 ms) - normal is typically <250-300 ms. This is a significant abnormality.
• Vertical precision at 0.45 Hz is elevated (156 / 136) suggesting dysmetria (overshoot/undershoot of eye to target).
• Interpretation: Vertical saccadic abnormality - this is associated with central (cerebellar or brainstem) dysfunction, not peripheral vestibular disease.

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2. Smooth Pursuit

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3. Optokinetic Test (OKN)

• Horizontal OKN gains are normal bilaterally.
• Bottom-to-top (upward) OKN is reduced, consistent with the downward gaze pursuit abnormality noted above.
• No asymmetry in horizontal OKN, which argues against a unilateral peripheral lesion being the sole etiology.

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4. Spontaneous Nystagmus

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5. Head-Shake Nystagmus

• All values absent / not recorded (Slow Phase Velocity = -, Amplitude = -).
• No post-head-shake nystagmus elicited. This can occur with bilateral peripheral hypofunction or be an incidental finding.

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6. Gaze Tests

• Gaze-evoked nystagmus in left gaze (with and without fixation), most prominent in the right eye.
• The nystagmus without fixation in left gaze is significantly amplified (13.63 °/s), indicating fixation suppression is intact (a peripheral feature), but the directionality and presence of vertical component favor a central etiology.
• No symmetric gaze-evoked nystagmus in all directions (which would indicate cerebellar gaze-holding failure).

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7. Dix-Hallpike Test

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8. McClure-Pagnini (Supine Roll) Test

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9. Subjective Visual Vertical (SVV)

• Normal SVV is ±2°.
• There is a wide variability (9° range) between clockwise and anticlockwise trials, suggesting inconsistency or a dynamic SVV disorder.
• The mean deviation is approximately -1.5°, which is borderline.
• SVV abnormalities indicate utricular dysfunction or central otolithic pathway dysfunction.

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Summary of Abnormal Findings

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Diagnosis

Central Vestibular Dysfunction

1. Primary diagnosis: Central Vestibulopathy - involving the brainstem (pontomedullary or pontocerebellar region) and/or cerebellum.
2. Differential considerations given the patient's age (77 years):
   • Cerebellar degeneration (age-related or spinocerebellar ataxia)
   • Posterior fossa vascular lesion - vertebrobasilar insufficiency, small brainstem/cerebellar infarct (especially given age and risk profile)
   • Cerebellar or brainstem mass lesion (less likely but cannot be excluded without imaging)
   • Multiple system atrophy (MSA) or other neurodegenerative condition affecting the oculomotor system
3. BPPV is excluded (negative Dix-Hallpike and Roll tests).
4. Isolated peripheral vestibulopathy is excluded by the presence of central oculomotor signs (impaired smooth pursuit, vertical saccadic abnormalities).

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Clinical Recommendations

1. Urgent MRI brain with contrast (posterior fossa protocol) - to rule out brainstem/cerebellar infarct, mass, or degenerative changes.
2. Neurology or neurotology referral for comprehensive evaluation.
3. Cardiovascular risk assessment - given age 77, vascular etiology must be worked up (BP, lipids, carotid Doppler, cardiac evaluation).
4. Falls risk assessment and vestibular rehabilitation should be considered once imaging is reviewed.

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Note: This interpretation is based on objective VNG data and should be correlated with clinical history, symptoms (dizziness, imbalance, gait disturbance), neurological examination, and imaging. A formal physician interpretation is required for clinical decision-making.

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VNG (Videonystagmography) Report - Interpretation

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Test-by-Test Analysis

1. Saccades

• Horizontal saccade velocities, precision, and latencies are within acceptable range for age 74.
• Vertical saccade latencies are significantly prolonged at both 0.3 Hz (360/381 ms) and 0.45 Hz (338/362 ms). Normal vertical saccade latency is typically <280 ms.
• Vertical saccade velocities are also notably reduced (~200-255 °/s vs. expected >400 °/s for this age group).
• Interpretation: Vertical saccadic slowing with prolonged latency - a central oculomotor sign involving brainstem (pontine/mesencephalic) or cerebellar pathways.

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2. Smooth Pursuit

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3. Optokinetic Test (OKN)

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4. Spontaneous Nystagmus

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5. Head-Shake Nystagmus

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6. Hyperventilation-Induced Nystagmus

• Demyelinating lesions (e.g., MS plaques)
• Partially compensated peripheral lesions (acoustic neuroma)
• Perilymphatic fistula
• Compression of the VIIIth nerve

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7. Valsalva Tests

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8. Gaze Tests

• No gaze-evoked nystagmus with fixation - all gaze positions are clean with fixation. This is important: it rules out a gaze-holding failure (cerebellar gaze-evoked nystagmus) and suggests fixation suppression of nystagmus is working.
• Nystagmus emerges at center and right gaze without fixation - left-beating horizontal nystagmus (SPV -9.57 °/s at center, -4.33 °/s at right) becomes visible only when fixation is removed. The ability of fixation to suppress nystagmus is a peripheral feature.
• The nystagmus direction (left-beating, right-eye dominant) is consistent with the HSN finding, pointing to right-sided peripheral hypofunction.

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9. Dix-Hallpike Test

• Dix-Hallpike RIGHT supine position: NEGATIVE (no nystagmus when hanging right - which tests the right posterior canal).
• Dix-Hallpike LEFT supine position: Positive - vertical nystagmus elicited in right eye when head extended and turned left (tests left posterior canal). SPV 3.32 °/s with 0.76 Hz. Although modest in amplitude, this represents provoked positional nystagmus with the left Dix-Hallpike maneuver.
• The nystagmus seen in the sitting positions (before and after hanging) likely reflects the baseline directional preponderance being modulated by head position.
• Partial left posterior canal involvement cannot be excluded, though values are modest and could also represent a canal paresis-related directional preponderance in positional testing.

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10. McClure-Pagnini (Supine Roll) Test

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11. Head Position Tests (Static)

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12. Subjective Visual Vertical (SVV)

• All values are within or at the boundary of normal (±2°).
• Mean deviation ~+0.67° (rightward tilt) - essentially normal.
• No significant otolithic asymmetry detected by SVV.

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Summary Table of Abnormalities

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Diagnosis

Primary Diagnosis: Right-Sided Peripheral Vestibular Hypofunction (Chronic/Compensated)

1. Left-beating post-head-shake nystagmus (SPV -5 to -6.5 °/s) - left-beating HSN indicates right vestibular hypofunction
2. Left-beating nystagmus without fixation at center and right gaze - fixation suppression intact (peripheral feature)
3. Strong direction-fixed left-beating positional nystagmus with head yaw right (SPV -23 °/s) - Alexander's law: nystagmus beats away from the lesion side
4. Absence of spontaneous nystagmus with fixation - consistent with compensated peripheral vestibular loss

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Secondary Finding: Central Oculomotor Involvement

1. Vertical saccadic slowing and prolonged latency (360-380 ms) - involves brainstem vertical gaze pathways
2. Symmetrically reduced smooth pursuit - especially at higher frequencies
3. Vertical OKN fast phases - impaired central vertical vestibulo-ocular reflex
4. Hyperventilation-induced nystagmus - may indicate retrocochlear involvement or demyelination

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Additional Finding: Possible Atypical Positional Component

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Clinical Recommendations

1. MRI brain/posterior fossa with contrast and FLAIR sequences - to evaluate for brainstem/cerebellar ischemia, demyelinating plaques, or cerebellopontine angle mass given the vertical saccadic slowing and hyperventilation-induced nystagmus.
2. Caloric testing (bithermal) - to quantify the right-sided canal paresis percentage and confirm the peripheral hypofunction side definitively (if not already done).
3. Audiometry / VEMP testing - to assess cochlear and otolithic (saccule/utricle) function in both ears and differentiate vestibular neuritis from Meniere's disease or retrocochlear pathology.
4. Epley maneuver for left posterior canal - if the positional nystagmus on DH left is confirmed as BPPV on clinical re-examination.
5. Vestibular rehabilitation - given the chronic right-sided hypofunction, a structured balance rehabilitation program is indicated.
6. Neurotology / neurology referral for the central oculomotor findings.

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Note: This is an objective data-based interpretation of VNG findings and must be correlated with clinical history, symptom onset, prior episodes, audiological evaluation, and imaging. Physician clinical correlation is required for final diagnosis and management.

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Could This Be Vertebrobasilar Dolichoectasia?

What is VBD?

1. Direct compression of cranial nerves (especially CN VIII - vestibulocochlear, CN VII, CN VI, CN V)
2. Brainstem compression - particularly the pons and medulla
3. Perforator ischemia - small brainstem perforating arteries get stretched or occluded
4. CSF flow obstruction
5. Embolic or thromboembolic events from sluggish flow in the dilated vessel

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How Well Does VBD Fit This Patient's VNG Profile?

Features in THIS report that SUPPORT VBD:

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The "Classic VBD Triad" - Does He Fit?

1. Unilateral sensorineural hearing loss - needs audiometry to confirm
2. Tinnitus - clinical history needed
3. Episodic vertigo / vestibular hypofunction - the VNG clearly shows right-sided hypofunction

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What Would Clinch the Diagnosis?

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Key Differentiator from Simple Vestibular Neuritis

• Prominent spontaneous nystagmus (right-beating acutely, left-beating in compensation)
• Normal saccades
• Normal smooth pursuit (may be mildly reduced acutely)
• No hyperventilation-induced nystagmus
• No vertical positional nystagmus in atypical positions

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Bottom Line

• The combination of right peripheral vestibular hypofunction + central oculomotor signs
• Hyperventilation-induced nystagmus (suggesting neurovascular compression)
• Strong atypical positional nystagmus
• Age and sex of the patient

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Differential Diagnosis Analysis

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DIFFERENTIAL 1: Vertebrobasilar Insufficiency (VBI)

What is VBI?

VNG Evidence FOR VBI in this patient:

VNG Evidence AGAINST Pure VBI:

• VBI typically presents with episodic symptoms - the VNG shows a fixed, compensated pattern suggesting structural damage rather than purely transient ischemia
• Pure VBI rarely produces persistent post-head-shake nystagmus of this degree without a structural lesion

VBI Verdict: HIGH PROBABILITY - especially as a mechanism operating on a background of atherosclerosis ± VBD

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DIFFERENTIAL 2: Vestibular Neurovascular Cross-Compression (NVC)

What is NVC?

VNG Evidence FOR NVC in this patient:

The HVIN finding is the smoking gun here:

• Horizontal HVIN beating TOWARD the lesion = demyelinating/irritative lesion (CN VIII NVC, MS plaque)
• Horizontal HVIN beating AWAY from lesion = hypofunction/destructive lesion
• Vertical HVIN = central pathway involvement (brainstem)

NVC Verdict: HIGH PROBABILITY - particularly as a component of underlying VBD

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DIFFERENTIAL 3: Vertebrobasilar Dolichoectasia (VBD)

Unifying Power of VBD:

• VBD → mechanical vessel compression of CN VIII → NVC
• VBD → sluggish flow, perforator stretch, embolism → VBI
• VBD → brainstem indentation → central oculomotor signs

Additional VNG markers supporting VBD specifically:

VBD Verdict: HIGH PROBABILITY - leading diagnosis

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DIFFERENTIAL 4: Antidepressant Disorientation Syndrome (ADS)

What is ADS?

VNG Evidence FOR ADS in this patient:

VNG Evidence AGAINST ADS as the SOLE diagnosis:

• Antidepressants do NOT cause asymmetric peripheral hypofunction - they would not produce the unilateral left-beating HSN, yaw-right directional preponderance, or the right-sided hypofunction pattern seen here
• Antidepressants do NOT cause hyperventilation-induced nystagmus - this is a structural sign
• Antidepressants do NOT cause strong positional nystagmus of the magnitude seen (-23 °/s with yaw right)

ADS Verdict: MODERATE PROBABILITY as a CONTRIBUTING FACTOR only - not sufficient as a standalone diagnosis, but if the patient is on antidepressants, they are likely amplifying/unmasking the underlying structural vestibular pathology

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Integrated Differential Diagnosis Summary

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The Most Likely Unified Diagnosis

Vertebrobasilar dolichoectasia with secondary right CN VIII neurovascular compression and posterior circulation perforator ischemia (VBI component), with possible pharmacological amplification of oculomotor deficits if antidepressants are being taken.

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Recommended Investigations to Differentiate

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Clinical note: In an elderly male with this VNG pattern, the combination of VBD + NVC + VBI represents a neurovascular continuum - not three separate diseases but one arteriopathic process expressing itself at multiple levels of the posterior fossa. Antidepressant review is a low-cost, reversible intervention that should be part of the workup regardless of the primary diagnosis.