Videonystagmography (VNG) Report - Detailed Diagnosis

Summary of Findings by Test Module

1. Saccade Testing

• Saccade velocities are within the lower-normal to normal range for most runs, though right eye vertical velocity (284-320 °/s at 0.3 Hz) falls slightly below the lower limit of 350 °/s. This is consistent with age-related slowing in a 78-year-old.
• Latency is mildly prolonged in several runs (up to 352 ms vertical right eye, 285 ms horizontal right eye), again consistent with age-related increase. However, persistent latency >260-270 ms can indicate basal ganglia, brainstem, or cerebellar involvement.
• Precision values are notably reduced (38-56 range, well below the 100% target). Low precision reflects dysmetria - inaccurate saccadic targeting. This implicates cerebellar or its pathway dysfunction.
• Impression: Mildly abnormal saccades - low precision (dysmetria) and mildly prolonged latency, suggesting cerebellar involvement cannot be excluded. Age-related change is contributory but does not fully account for the pattern.

2. Smooth Pursuit Testing

• Smooth pursuit gains are significantly reduced in both horizontal and vertical planes, in both eyes. Normal gain should be >0.8 for horizontal tracking.
• Gains of 0.10-0.66 represent moderate-to-severe impairment, especially the left eye horizontal 0.4 Hz (gain 0.10), which is in the absent range (<0.2), indicating a likely central nervous system disturbance.
• Vertical gains are uniformly very low (0.19-0.27), which is abnormally low even accounting for the typically lower vertical gains compared to horizontal.
• Reduced pursuit gain in an elderly patient can have multiple causes: central lesion (cerebellum, pontine nuclei, cortex), medications, or attention. However, the severity and bilateral symmetric pattern - particularly the near-absent left eye pursuit at 0.4 Hz - is beyond typical age-related decline.
• Impression: Significantly abnormal smooth pursuit bilaterally, suggestive of central vestibular/oculomotor pathway dysfunction, likely involving the cerebellum (vestibulocerebellum/paraflocculus) or brainstem.

3. Optokinetic Testing (OKN)

• Left eye OKN responses are symmetrical and near-normal. The absence of right eye OKN data limits full interpretation.
• Normal OKN in the recorded eye provides some reassurance against severe cortical or brainstem lesion. However, given the smooth pursuit abnormalities, the OKN result should be interpreted cautiously.
• Impression: Incomplete data; left eye OKN appears normal.

4. Spontaneous Nystagmus (Light and Dark)

• No spontaneous nystagmus detected in light or dark conditions.
• No head-shake nystagmus detected.
• Impression: Absent spontaneous nystagmus. This argues against an acute active unilateral peripheral vestibular lesion (e.g., vestibular neuritis in its active phase).

5. Gaze Testing (With and Without Fixation)

• Gaze tests with fixation (center, left, right, up, down): No pathological nystagmus detected in any direction.
• Gaze without fixation: Most positions are negative. However, "Gaze Down - Without Fixation" showed:
  • Left eye: Slow Phase Velocity = 6.15 °/s (horizontal); 2.07 °/s (vertical)
  • Amplitude: 2.49° horizontal; 1.86° vertical
  • Fast Phase Direction: 323.34°
  • Frequency: 1.89 Hz

• Downward gaze-evoked nystagmus without fixation in the left eye, with a fast phase direction of ~323° (oblique - predominantly leftward/upward). This is a subtle but clinically relevant finding.
• Gaze-evoked nystagmus (appearing only without fixation) is most consistent with central vestibular or cerebellar dysfunction, particularly when associated with the pursuit abnormalities seen here.

6. Positional Testing - Dix-Hallpike (Right and Left)

• Dix-Hallpike Right (all positions - Sit Head Right, Supine Head Ext & Right, return): No nystagmus detected (all parameters "-").
• Dix-Hallpike Left (all positions - Sit Head Left, Supine Head Ext & Left, return): No nystagmus detected.
• Impression: Dix-Hallpike bilateral negative. This argues against posterior semicircular canal BPPV.

7. Positional Testing - Yacovino Maneuver (Anterior Canal BPPV Protocol)

• The Supine Head Hanging (90° extension) position during the Yacovino protocol provoked nystagmus in the left eye with a fast phase direction of 140.63° (oblique - consistent with a downbeat and torsional component). This is the pathognomonic response for Anterior Canal BPPV (AC-BPPV).
• Nystagmus also persisted in the Supine End position (slow phase velocity -5.67 °/s vertically at 0.9 Hz).
• The Yacovino maneuver is specifically designed to diagnose and treat Anterior Semicircular Canal BPPV, which is the rarest form of BPPV (~1-3% of all BPPV cases). Unlike posterior canal BPPV, it does not require side determination as both anterior canals are stimulated simultaneously in the head-hanging position.
• In AC-BPPV, the Dix-Hallpike can be negative or show only faint downbeat nystagmus, while the Yacovino supine head-hanging position elicits a clear downbeat (and sometimes torsional) nystagmus - exactly matching this patient's findings.

8. Positional Testing - McClure-Pagnini (Lateral Canal BPPV Protocol)

• Impression: McClure-Pagnini negative bilaterally. Lateral (horizontal) semicircular canal BPPV is not present.

9. Subjective Visual Vertical (SVV)

• The anticlockwise trial deviation of -12° (leftward) is markedly abnormal. Normal SVV lies within ±2° of true vertical.
• A 12° deviation is a strongly abnormal SVV result, indicating significant otolith (utricular) dysfunction or central vestibular pathway abnormality.
• SVV tilt contralateral to the affected ear suggests the pathological side is the right utricle/right otolith pathway (SVV tilts away from the affected side in peripheral lesions, toward the affected side in certain central lesions). The variability between clockwise (near normal, +1°) and anticlockwise (-12°) trials may suggest measurement variability or positional effect.
• The blank background result (0°) is normal, suggesting some visual context dependency.
• Impression: Significantly abnormal SVV - consistent with utricular otolith dysfunction.

Overall Diagnostic Summary

Primary Diagnosis:

• Positive Yacovino maneuver (supine head-hanging position at 90° extension provoked nystagmus with fast phase direction at ~140° - consistent with downbeat/oblique nystagmus)
• Negative Dix-Hallpike bilaterally (typical of AC-BPPV as posterior canal is not involved)
• Negative McClure-Pagnini (ruling out lateral canal BPPV)
• Recommended treatment: Yacovino Deep Head-Hanging maneuver (canalith repositioning)

Secondary/Associated Findings:

• Markedly abnormal SVV (-12° deviation on anticlockwise trial), far exceeding the normal ±2° threshold
• This may represent concurrent otolith involvement alongside canalith disease

• Severely reduced smooth pursuit gain bilaterally (particularly near-absent left eye pursuit at 0.4 Hz)
• Low saccade precision (dysmetria pattern)
• Mildly prolonged saccade latency
• Gaze-evoked nystagmus (downward direction, without fixation)
• In a 78-year-old, age-related cerebellar and cortical changes are the most likely explanation, but central vestibular pathology (small vessel disease, cerebellar degeneration) must be considered

Clinical Recommendations

1. Canalith Repositioning: Perform the Yacovino (Deep Head-Hanging) maneuver for AC-BPPV treatment. Success rate is approximately 50-85% per session; repeat if symptoms persist.
2. Neurological Evaluation: The combination of severely impaired smooth pursuit, reduced saccadic precision, prolonged latency, and gaze-evoked nystagmus warrants neurology/neuro-otology consultation to exclude:
   • Cerebellar atrophy or small vessel ischemic disease
   • Central positional nystagmus (must be differentiated from AC-BPPV)
   • MRI brain with posterior fossa sequences (FLAIR, DWI) is advisable
3. Caloric Testing: Notably absent from this report. Caloric irrigation would help quantify unilateral/bilateral canal weakness and further characterize the vestibular lesion side.
4. Vestibular Rehabilitation: Given the otolith dysfunction (abnormal SVV) and central oculomotor impairment, a structured vestibular rehabilitation program is recommended to reduce fall risk - especially important in this 78-year-old patient.
5. Medication Review: Several medications can suppress smooth pursuit gain (vestibular sedatives, benzodiazepines, anticonvulsants). Medication history should be reviewed before attributing all smooth pursuit abnormality to structural pathology.

Important Note: This report interpretation is provided for clinical educational context. The treating physician and/or vestibular specialist should correlate these findings with the patient's full history, symptom duration, and clinical examination. Central positional nystagmus (from cerebellar or brainstem pathology) can mimic AC-BPPV and must be carefully excluded before proceeding with repositioning maneuvers.