VNG (Videonystagmography) - Detailed Neurootological Analysis

• H/o one episode of vertigo (with back sensation) lasting 5-10 minutes, 1 week back
• C/o heaviness in the head
• C/o mild giddiness all the time

I. OCULAR MOTOR BATTERY

1. Saccade Test (0.3 Hz)

• Latency is significantly prolonged bilaterally (horizontal and vertical) - both eyes show latencies of 350-420 ms, well above the normal upper limit of ~250 ms. This suggests slowed saccadic initiation.
• Precision (accuracy) is reduced bilaterally, more so in the right eye (61-65% vs normal >85%). This indicates dysmetria - hypometric saccades (undershooting).
• Velocity: Right eye horizontal velocity (690 °/s) is at the high-normal/borderline range; left eye (952 °/s) is elevated (hypermtric saccadic velocity). Asymmetric horizontal velocities (ratio >2.0) suggest right-sided limitation.
• Combined finding: Prolonged latency + reduced accuracy (bilaterally) is consistent with central saccadic pathway dysfunction (cortical or cerebellar involvement) rather than peripheral vestibular disease.

2. Smooth Pursuit Test (0.2 Hz)

• Horizontal pursuit: Right eye gain is reduced (0.63 rightward, 0.67 leftward) - below the normal threshold of 0.7. Left eye gain is preserved. This asymmetry may reflect a right-sided pursuit defect or inter-ocular coordination issue.
• Vertical pursuit (upward): Severely reduced bilaterally - right eye 0.31, left eye 0.38. Both are significantly below the lower limit of normal (~0.5). Vertical upward smooth pursuit is markedly impaired.
• Vertical pursuit (downward): Borderline (0.61-0.70), mildly reduced.
• Clinical significance: Impaired vertical smooth pursuit (especially upward) strongly suggests central pathway involvement, particularly affecting the dorsal midbrain or pontine pursuit circuits. This finding combined with saccadic abnormalities makes a central vestibular etiology likely.

3. Optokinetic Test (OKN)

• Horizontal OKN: Symmetric and essentially within normal limits (L→R: 1.05/1.02; R→L: 0.80/0.80). No directional preponderance.
• Vertical OKN: Reduced in both directions (top-to-bottom and bottom-to-top gains: 0.63-0.77), below normal. This mirrors the vertical smooth pursuit impairment.
• Significance: The pattern of normal horizontal OKN but impaired vertical OKN is consistent with central (brainstem/midbrain) dysfunction. The symmetry of horizontal OKN argues against a unilateral peripheral vestibular lesion for this parameter.

II. NYSTAGMUS TESTS

4. Spontaneous Nystagmus

• No spontaneous nystagmus in light - fixation suppresses nystagmus effectively.
• Spontaneous nystagmus appears in darkness - vertical component (slow phase velocity -6.20°/s, downward) detected in the right eye at 0.60 Hz. Amplitude of -5.23° is clinically significant (above the 2.5°/s threshold).
• A downbeat slow phase (meaning upbeat fast phase nystagmus) emerging in darkness, suppressed by fixation, is a central nystagmus pattern. This is characteristic of conditions affecting the vestibulo-cerebellum (flocculus/nodulus) or brainstem.
• The fixation suppression index (FSI) is effectively positive here (nystagmus absent in light, present in dark), which paradoxically suggests some degree of central fixation suppression failure in a non-conventional pattern.

5. Head Shake Test (High Frequency)

6. Hyperventilation Test

III. GAZE TEST

7. Gaze-Evoked Nystagmus

• No gaze-evoked nystagmus in any position, with or without fixation.
• This argues against cerebellar degeneration (which typically produces gaze-evoked nystagmus), and against congenital nystagmus.
• Combined with the spontaneous dark nystagmus finding, this creates a nuanced picture suggesting a subclinical or partially compensated central vestibular disturbance.

IV. POSITIONAL TESTING

8. Dix-Hallpike Test

Right-Sided Dix-Hallpike

Left-Sided Dix-Hallpike

• The classic vertical-torsional paroxysmal nystagmus of posterior canal BPPV is absent in both Dix-Hallpike positions (no clear up-beating torsional nystagmus with latency, crescendo-decrescendo pattern).
• Low-grade horizontal nystagmus on the right Dix-Hallpike (sitting head right: SPV 1.21°/s) is subthreshold for classic BPPV criteria.
• The Sit Head Left return position showing horizontal left eye nystagmus (3.96°/s) may indicate a geotropic horizontal component which could suggest horizontal (lateral) canal BPPV or central positional nystagmus - but needs correlation.
• Overall, typical posterior canal BPPV is not confirmed by this VNG.

9. Head Position Tests (Static Positional)

• Significant positional nystagmus during Roll Left is the most clinically important finding in the positional battery.
• SPV of 16.25°/s with amplitude 6.70° in the right eye during left roll is well above the threshold for positional nystagmus (>2.5°/s considered significant; >5°/s strongly positive).
• Horizontal nystagmus on left roll (beating right = geotropic or ageotropic depending on fast phase direction) - the fast phase in the right eye beating toward the right while the head is rolled left suggests apogeotropic horizontal positional nystagmus OR right horizontal canal BPPV (cupulolithiasis variant).
• Absence of nystagmus on Roll Right (asymmetric response) further supports this being a right horizontal canal pathology or a right cupula anomaly.
• Roll left nystagmus that is direction-fixed and persists (not paroxysmal/transient) is more consistent with horizontal canal cupulolithiasis or central positional nystagmus.

V. SUBJECTIVE VISUAL VERTICAL (SVV)

• SVV is tilted to the right by 3° in the clockwise trial (above the ±2° normal threshold).
• The blank background trial shows +1° (within normal limits).
• A consistent rightward tilt of SVV (particularly the 3° clockwise deviation) suggests a left otolithic (utricular) imbalance - i.e., the patient's perceived vertical is shifted to the right, indicating the left labyrinth is relatively under-activating the otolith system or the right side is over-active.
• SVV tilt contralateral to the affected side: if SVV tilts right, the left otolith pathway is disrupted.
• This otolithic imbalance is consistent with left vestibular utricular dysfunction (possibly subtle or compensating), or a left-sided central otolithic pathway lesion.

VI. INTEGRATED INTERPRETATION

Summary Table of Abnormal Findings

VII. DIAGNOSIS (for Neurootologist)

Primary Diagnosis:

1. Impaired vertical smooth pursuit (up > down)
2. Prolonged saccadic latency and reduced precision bilaterally
3. Impaired vertical OKN
4. Spontaneous downbeat-component nystagmus in darkness (fixation-suppressed)

Secondary Diagnosis:

• Significant geotropic/apogeotropic horizontal positional nystagmus on Roll Left (SPV 16.25°/s, amplitude 6.70°)
• Absent nystagmus on Roll Right
• No classic posterior canal BPPV pattern on Dix-Hallpike

Contributing Finding:

• SVV tilted +3° to the right (exceeds ±2° threshold, implicating left utricle)

VIII. DIFFERENTIAL DIAGNOSIS TO CONSIDER

1. Vestibular Migraine - Most likely unifying diagnosis given the patient's age (36F), episodic vertigo lasting 5-10 minutes, constant background giddiness, head heaviness, and the pattern of central VNG abnormalities (migraine frequently causes central-pattern VNG findings including smooth pursuit, saccadic, and positional abnormalities). SVV tilt and spontaneous dark nystagmus are well-documented in vestibular migraine.
2. Multiple Sclerosis (demyelinating disease) - Must be excluded given bilateral saccadic latency prolongation, vertical smooth pursuit impairment, and central nystagmus pattern. An MRI brain with FLAIR sequences (especially posterior fossa, brainstem, periventricular) is mandatory.
3. Cerebellar Ataxia (early/subclinical) - The combination of saccadic dysmetria and impaired smooth pursuit warrants MRI of the posterior fossa.
4. Persistent Postural-Perceptual Dizziness (PPPD) with underlying central sensitization - The constant mild giddiness and head heaviness are consistent with this, possibly co-existing with the above.
5. Horizontal Canal BPPV (cupulolithiasis) - Explains the Roll Left positional nystagmus. Can be treated with BBQ roll or Appiani/Forced Prolonged Position maneuver.

IX. RECOMMENDATIONS

1. MRI Brain + posterior fossa with gadolinium and FLAIR - Rule out demyelinating plaques (MS), cerebellar pathology, cerebellopontine angle lesion, or brainstem lesion.
2. Audiological evaluation - Pure tone audiometry, speech audiometry, and tympanometry to assess cochlear/retrocochlear status.
3. Vestibular Evoked Myogenic Potentials (VEMP) - Cervical VEMP (saccule/inferior vestibular nerve) and Ocular VEMP (utricle/superior vestibular nerve) to further characterize otolithic function and localize the level of lesion.
4. Neurology/Neuro-otology consultation - For evaluation of possible vestibular migraine vs. early central pathology. Consider migraine history, family history, and photophobia/phonophobia during attacks.
5. Canalith Repositioning for Right Horizontal Canal BPPV - If right HC-BPPV (cupulolithiasis) is confirmed clinically, perform BBQ (Barbecue) roll maneuver or Forced Prolonged Position toward the unaffected (left) side.
6. Vestibular Rehabilitation Therapy (VRT) - Gaze stabilization exercises and habituation exercises to address central compensation deficits.
7. Repeat VNG - After 4-6 weeks of any treatment or rehabilitation to assess for change in positional nystagmus and ocular motor findings.

Key Clinical Correlation Note: The VNG findings (especially central ocular motor abnormalities + positional nystagmus + SVV tilt) in a 36-year-old female with episodic vertigo, constant giddiness, and head heaviness strongly point toward vestibular migraine as the most probable unifying diagnosis, with a superimposed right horizontal canal BPPV. Central organic pathology must be excluded by neuroimaging before confirming this diagnosis. No caloric test data was included in this VNG report - if available, caloric testing results should be integrated to assess unilateral canal weakness and directional preponderance.

NEUROLOGICAL DIAGNOSTIC REPORT

VNG-Based Neurology Referral Summary

PRESENTING COMPLAINTS

• Single episode of vertigo with "back sensation" lasting 5-10 minutes, 1 week prior
• Constant mild giddiness (continuous background)
• Heaviness of head (ongoing)

VNG FINDINGS RELEVANT TO NEUROLOGY

A. OCULAR MOTOR ABNORMALITIES (Central Markers)

1. Saccadic Eye Movements - ABNORMAL

• Bilaterally prolonged saccadic latency indicates slowed voluntary saccade initiation - a marker of dysfunction in the frontal eye fields (FEF), supplementary eye fields, or superior colliculus pathways
• Reduced precision (hypometric saccades) bilaterally, worse on the right, indicates saccadic dysmetria pointing toward cerebellar vermis or fastigial nucleus dysfunction

2. Smooth Pursuit - ABNORMAL (Central Pattern)

• Severely impaired vertical upward smooth pursuit (0.31/0.38) is a hallmark of dorsal midbrain dysfunction - specifically the posterior commissure, rostral interstitial nucleus of MLF (riMLF), or periaqueductal grey region
• Right-eye asymmetry in horizontal pursuit suggests additional right-sided PPRF (paramedian pontine reticular formation) or ipsilateral cerebellar involvement
• This pattern has high specificity for central nervous system pathology

3. Optokinetic Nystagmus (OKN) - ABNORMAL

• Horizontal OKN preserved; vertical OKN reduced in both directions
• Corroborates dorsal midbrain or pretectal involvement (Parinaud-spectrum dysfunction)

B. NYSTAGMUS FINDINGS

4. Spontaneous Nystagmus in Darkness - ABNORMAL

• Spontaneous downbeat-component nystagmus appearing only in darkness, suppressed by visual fixation
• Downbeat nystagmus is a localizing sign for the cranio-cervical junction or vestibulocerebellum - specifically the flocculus, nodulus, or inferior vermis dysfunction, or foramen magnum region pathology
• The fixation suppression of this nystagmus indicates the visual system can partially compensate - consistent with a subclinical or partially compensated central lesion

5. Gaze Test - Normal

• No gaze-evoked nystagmus in any direction (center, right, left, up, down) - with or without fixation
• Absence of gaze-evoked nystagmus makes active cerebellar degeneration or INO (internuclear ophthalmoplegia) less likely at present

C. POSITIONAL FINDINGS

6. Static Head Position - Roll Left - ABNORMAL

• High-velocity horizontal positional nystagmus on left roll, absent on right roll
• Asymmetric positional nystagmus can be peripheral (horizontal canal BPPV) or central (central positional nystagmus)
• The absence of the full bilateral BBQ-roll pattern, combined with the other central VNG markers, raises concern for central positional nystagmus

7. Dix-Hallpike - No Classic Posterior Canal BPPV

• No typical up-beating torsional nystagmus with latency and fatigability
• Low-grade horizontal positional nystagmus detected (subthreshold for classic BPPV)

D. SUBJECTIVE VISUAL VERTICAL (SVV)

• SVV tilted rightward in the clockwise condition indicates left otolithic (utricular) pathway dysfunction
• Central SVV tilt can occur with lesions anywhere from the left labyrinth → left vestibular nerve → left vestibular nuclei → thalamus (VPLc) → parietal cortex (PIVC - parieto-insular vestibular cortex)
• Right-deviated SVV with the other central markers points toward a left-sided central vestibular pathway lesion or left utricular dysfunction

NEUROLOGICAL DIAGNOSIS

PRIMARY DIAGNOSIS:

⚠ Central Vestibular Syndrome - Most Likely Vestibular Migraine

1. Age 36, female - peak demographic for vestibular migraine
2. Episodic vertigo (5-10 min duration - classic for vestibular migraine; peripheral BPPV is seconds, Meniere's is 20 min-hours, TIA is abrupt)
3. Constant interictal dizziness and head heaviness (characteristic of vestibular migraine interictal phase)
4. VNG shows multiple central ocular motor abnormalities (impaired vertical pursuit, saccadic latency prolongation, vertical OKN reduction) - all well-documented in vestibular migraine even interictally
5. Spontaneous dark nystagmus (downbeat component) - seen in vestibular migraine due to cerebellar/brainstem hyperexcitability
6. SVV tilt - documented in vestibular migraine attacks and interictal periods
7. No hearing loss pattern to suggest Meniere's; no acute unilateral deafferentation to suggest vestibular neuritis

• At least 5 episodes of vestibular symptoms of moderate/severe intensity (needs history)
• Current or past history of migraine (to be elicited)
• One or more migraine features during vestibular episodes (to be confirmed)
• Not better accounted for by another vestibular disorder (central pathology must be excluded by MRI)

SECONDARY DIAGNOSIS:

Right Horizontal Canal BPPV (Cupulolithiasis variant)

• Roll Left positional nystagmus (16.25°/s horizontal, right eye) with no nystagmus on Roll Right
• Likely co-existing peripheral BPPV superimposed on the central vestibular syndrome
• Treatable with BBQ Roll (Lempert) maneuver or Forced Prolonged Position

DIAGNOSES TO EXCLUDE (Urgent):

INVESTIGATIONS RECOMMENDED

Urgent / Priority

1. MRI Brain with Gadolinium - FLAIR, T2, DWI, T1 post-contrast sequences; dedicated posterior fossa/brainstem cuts; cranio-cervical junction views
2. MRA Vertebrobasilar System - to exclude posterior circulation stenosis/TIA risk

Second Line

1. Visual Evoked Potentials (VEP) - to exclude demyelination (MS)
2. Brainstem Auditory Evoked Responses (BAER/ABR) - assess brainstem conduction
3. Ocular VEMP (oVEMP) + Cervical VEMP (cVEMP) - characterize otolithic pathway (SVV tilt suggests left utricular dysfunction)
4. Pure Tone Audiometry + Tympanometry - exclude retrocochlear pathology
5. Fasting blood glucose, CBC, thyroid function, lipid profile, B12 - metabolic causes of dizziness

If MRI Normal / History Supports:

1. International Headache Diary - document migraine features, triggers, aura
2. Neurology OPD - formal evaluation for vestibular migraine vs. other central vestibular disorder

SUMMARY FOR NEUROLOGIST

Pooja, 36F, presents with episodic vertigo (5-10 min), constant giddiness, and head heaviness. VNG reveals a central vestibular pattern: bilaterally prolonged saccadic latency, severely impaired vertical upward smooth pursuit (gain 0.31-0.38), impaired vertical OKN, spontaneous downbeat nystagmus in darkness (SPV -6.20°/s) suppressed by fixation, rightward SVV tilt (+3°), and asymmetric horizontal positional nystagmus on Roll Left (16.25°/s). No classic peripheral BPPV pattern. The clinical and VNG profile is most consistent with Vestibular Migraine with a co-existing right horizontal canal BPPV. Central organic pathology (MS, posterior fossa lesion, Chiari, vertebrobasilar TIA) must be urgently excluded by MRI brain with gadolinium + MRA vertebrobasilar circulation before initiating vestibular migraine management.