Signature ENG what is it ?
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Signature ENG electrooculography software NBM optokinetic nystagmus
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Signature ENG vestibular testing software "Signature ENG" NBM systems
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Signature ENG NBM software vestibular
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"Signature ENG" NBM vestibular software oculomotor testing system
Based on your image and question, here is what Signature ENG is:
Signature ENG — What It Is
Signature ENG is a vestibular/oculomotor testing software platform developed by NBM (the ©NBM watermark is visible in your screenshot). It is used in audiology and neurotology clinics to record and analyze electronystagmography (ENG) — the objective measurement of eye movements (nystagmus) to assess the vestibular (balance) and oculomotor systems.
What the Image Shows
Your screenshot displays two traces typical of an ENG study:
- Red trace (top) — likely the eye movement signal from one eye (e.g., right eye), showing rhythmic nystagmus-like waveforms
- Blue trace (bottom) — the other eye (labeled "Left Eye" with a value of 18.04 in the tooltip), showing a lower-amplitude, higher-frequency oscillation
- "44" on the cursor line = likely a time marker or SPV (slow-phase velocity) value in °/sec
- The drag-to-scroll scrollbar = characteristic of ENG software review mode
What ENG / Signature ENG Tests
The ENG battery typically includes:
| Test | What It Evaluates |
|---|---|
| Spontaneous nystagmus | Baseline vestibular asymmetry |
| Gaze nystagmus | Central vs. peripheral pathology |
| Positional/Positioning nystagmus | BPPV and semicircular canal function |
| Optokinetic (OKN) | Central vestibulo-ocular pathways |
| Smooth pursuit | Cerebellar/central function |
| Saccades | Brainstem integrity |
| Bithermal caloric test | Unilateral vestibular weakness (inner ear) |
ENG records these movements via skin electrodes around the eyes, exploiting the eye's natural corneoretinal electrical potential — the eye acts as a dipole, with the cornea positive and retina negative.
Clinical Use
Signature ENG / NBM systems are used to diagnose:
- Ménière's disease
- Vestibular neuritis / labyrinthitis
- BPPV (benign paroxysmal positional vertigo)
- Central vestibular disorders (cerebellar stroke, MS)
- Ototoxicity monitoring
The value 18.04°/sec visible in your trace likely represents the slow-phase velocity (SPV) of the nystagmus at that point — a key quantitative metric in ENG interpretation. Values above ~6–7°/sec are generally considered abnormal for spontaneous nystagmus.
Type of nystagmus?
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Here is a comprehensive classification of nystagmus types, relevant to ENG interpretation:
Types of Nystagmus
1. By Waveform (Fundamental Division)
| Type | Description | Origin |
|---|---|---|
| Jerk nystagmus | Slow drift away + fast corrective saccade (named by direction of fast phase) | Peripheral or central |
| Pendular nystagmus | Equal velocity in both directions — sinusoidal, like a pendulum | Always central (brainstem/cerebellum) |
Jerk nystagmus is further classified by the shape of the slow phase on ENG tracings:
- Linear (constant velocity) → vestibular dysfunction (peripheral or central)
- Decreasing velocity exponential → "leaky" neural integrator → gaze-paretic nystagmus
- Increasing velocity exponential → infantile nystagmus syndrome (INS) or congenital nystagmus
2. By Direction
| Direction | Key Association |
|---|---|
| Horizontal | Most common; peripheral vestibular (unidirectional) |
| Vertical — Upbeat | Pontomesencephalic lesion |
| Vertical — Downbeat | Cervicomedullary junction / flocculus lesion |
| Torsional/Rotatory | Often with BPPV or lateral medullary infarct |
| Mixed horizontal-torsional | Peripheral vestibular disease |
| Seesaw nystagmus | Mesodiencephalic junction / chiasm |
3. By Clinical Context (ENG Battery)
| ENG Test | Nystagmus Type Sought |
|---|---|
| Spontaneous | Baseline nystagmus without fixation (>6–7°/sec SPV = abnormal) |
| Gaze-evoked | Nystagmus appearing only on lateral/vertical gaze — "leaky integrator" |
| Positional | Elicited by sustained head position (e.g., Dix-Hallpike) |
| Positioning (BPPV) | Transient, fatigable; torsional-vertical; latency ~5 sec; lasts <30 sec |
| Caloric-induced | Unidirectional jerk induced by hot/cold irrigation — tests horizontal SCC |
| Optokinetic (OKN) | Normal reflex nystagmus to moving visual field; asymmetry = central pathology |
| Post-rotatory | Vestibuloocular reflex (VOR) testing |
4. By Origin (Localization)
| Origin | Characteristics |
|---|---|
| Peripheral (labyrinth/CN VIII) | Unidirectional, horizontal or horizontal-torsional; suppressed by fixation (Frenzel lens reveals it); beats away from lesion (Alexander's law applies) |
| Central (brainstem/cerebellum) | Direction-changing, vertical, or pendular; not suppressed by fixation; may have normal calorics |
Regarding Your ENG Trace
The waveform in your Signature ENG screenshot — rhythmic, repetitive, moderate-amplitude — is consistent with jerk nystagmus with a linear slow phase, most typical of vestibular (peripheral) nystagmus. The SPV of 18.04°/sec on the left eye is significantly above the normal threshold (~6–7°/sec), indicating active vestibular imbalance at that moment in the recording.
- Adams and Victor's Principles of Neurology, 12th Ed.
- Bradley and Daroff's Neurology in Clinical Practice
- K.J. Lee's Essential Otolaryngology
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