More of subjective dizziness. And pls tell me what is this left eye receding tells “sudden spike” patient does not have eye blinking during tests.
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Now I have enough context from the textbooks to provide a thorough interpretation. Let me synthesize everything from the VNG report.
VNG Report Interpretation — Mrs. Darshana Jain, 74F
Two questions addressed:
1. "Subjective Dizziness" in the context of this report
The patient's complaint is subjective dizziness (a sense of unsteadiness/floating/lightheadedness without true spinning vertigo). Looking at the VNG results, the relevant finding is:
Gaze Test: Center – Without Fixation
- Right eye: Slow Phase Velocity 4.26°/s, Amplitude 3.03°, Frequency 0.90 Hz
- This is a low-velocity spontaneous nystagmus present only when fixation is removed (eyes closed / in darkness)
This pattern — nystagmus that emerges without fixation but is suppressed when fixation is present — is consistent with a compensated peripheral vestibular lesion (chronic unilateral hypofunction). The right eye shows residual drift at rest; the brain has partially compensated (hence no nystagmus in light), but in the dark, without the visual anchor, the asymmetric vestibular tone becomes unmasked. The patient perceives this as non-rotational, subjective dizziness rather than spinning vertigo — precisely because compensation is underway but incomplete.
All gaze-fixed positions (center, left, right, up, down — all with fixation) showed no nystagmus, confirming effective fixation suppression and ruling out active central pathology or acute peripheral lesion.
2. "Left Eye Receding / Sudden Spike — Patient Does Not Blink During Tests"
This refers to the left eye data across multiple subtests showing anomalously high or implausible values. Here is the pattern:
| Test | Left Eye Value | Right Eye Value | Comment |
|---|---|---|---|
| Horizontal Saccade Velocity | 2142°/s | 190°/s | Physiologically impossible |
| Vertical Saccade Velocity | 614°/s | 151°/s | Far above normal range |
| Horizontal Saccade Precision | 150 | 13.8 | Extreme dysmetria-like value |
| Smooth Pursuit Horizontal Gain | 0.07 | 0.82–1.00 | Essentially zero |
| Smooth Pursuit Vertical Gain | 0.12–0.21 | 0.76–0.82 | Near-zero |
What is happening:
In VNG (videooculography), the software tracks the pupil position frame by frame using infrared cameras. When the patient does not blink, the eyelid is held in an unnatural static position. When it does move (even a partial blink, a twitch, or eyelid margin shift), the camera momentarily loses the pupil or tracks the eyelid instead — generating a sudden artefactual spike in the recorded eye position trace. The algorithm registers this as an instantaneous large displacement, which when differentiated to calculate velocity, yields a spuriously enormous velocity value (e.g., 2142°/s, which is biologically impossible — real saccades peak at ~600–700°/s maximum).
Why specifically the left eye:
The left eye lens/camera may have had a suboptimal fit, reduced aperture capture, or partial corneal reflection interference. In a 74-year-old, ptosis, asymmetric palpebral fissure, or deeper set eye on the left side can cause exactly this — the infrared camera partially occludes the pupil window, making the system hypersensitive to any lid or periocular movement rather than tracking the true pupil centre.
The "receding" appearance on the trace is the artefactual downward baseline drift on the Left Horizontal channel (visible in Smooth Pursuit plots) — the left eye channel hovers near its floor (0–7 on the scale) while the right eye tracks the sinusoidal target normally (gain 0.82–1.0). This is not true pursuit failure of the left eye neurologically — it is the camera failing to track the left pupil.
Key supporting evidence:
- Left eye smooth pursuit gain = 0.07 (both horizontal and vertical) — this means the left eye appears to follow the target with only 7% accuracy, which would imply a completely paralysed left eye. Clinically this is absent; no left gaze palsy is mentioned.
- No spontaneous nystagmus recorded from left eye in any condition — if there were true left eye oculomotor dysfunction, nystagmus patterns would differ between eyes.
- Saccade latency for left eye (322 ms horizontal, 328 ms vertical) is in a relatively normal range — only the velocity is impossibly high (artefact), not the latency.
Clinical bottom line for the left eye data: The left eye channel data is unreliable throughout this test due to poor pupil tracking, likely from absence of blink (eyes are held wide open, causing dryness and lid position artefacts) combined with the camera geometry on the left side. The right eye data is the valid channel for interpretation.
Overall VNG Interpretation Summary
| Domain | Finding | Significance |
|---|---|---|
| Spontaneous nystagmus (light) | None | No active acute lesion |
| Spontaneous nystagmus (dark) | Low-velocity right eye drift (SPV 4.26°/s) | Compensated peripheral lesion (right side) |
| Gaze nystagmus | None in all positions with fixation | No central pathology |
| Saccades (right eye) | Velocity 190°/s (H), 151°/s (V); latency 470 ms (H) — prolonged | Delayed saccade initiation; worth correlating clinically |
| Smooth pursuit (right eye) | Gain 0.82–1.0 (H), 0.76–0.82 (V) | Borderline-normal for age 74 |
| OKN | Gain 0.41–0.59 — symmetrically reduced | Age-related reduction; no directional asymmetry |
| SVV Clockwise | +8° (rightward tilt) | Abnormal — otolith asymmetry, tilt toward lesioned side |
| SVV Anticlockwise | −2° | Near-normal on second pass |
| SVV Blank background | 90° (Trial 1, 0 s) → −3° (Trial 2) | Trial 1 is artefact (patient set it immediately, no deliberation); Trial 2 borderline |
| Left eye data | Artefactual throughout | Not interpretable |
SVV finding (Clockwise trial: +8°) is clinically significant — normal is ≤2–3°. An 8° rightward tilt indicates the right otolith (utricular) function is dominant, suggesting left utricular hypofunction or tilt of the subjective gravitational vertical toward the right. This corroborates the right-eye spontaneous nystagmus (slow phase right, fast phase could be left) seen in darkness.
Recommended next step: Caloric testing (not performed here) to quantify unilateral canal paresis, and correlation with the patient's clinical history of dizziness onset, whether positional or constant.
— Cummings Otolaryngology Head and Neck Surgery, Quantitative Testing section (p. 3186–3191); Clinical Importance of Otolith Function (p. 3167)
Give the full detailed VNG REPORT
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