vestibular neuronitis in detail for 50 marks with diagram and flow charts from Scott Brown, Cummings, stell and marans, Zakir Hussain, dhingra, hazarika and related articles with recent advances according to rguhs university

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I now have sufficient retrieved content and will compose a comprehensive 50-mark answer drawing from all major ENT textbooks and recent literature.

VESTIBULAR NEURONITIS

A Comprehensive 50-Mark Answer

References: Scott-Brown's Otorhinolaryngology (8th ed.), Cummings Otolaryngology (7th ed.), Stell & Maran's Head & Neck Surgery, Dhingra's Diseases of Ear, Nose & Throat, Hazarika's Textbook of ENT, Zakir Hussain's Textbook of ENT, and Recent Literature

1. INTRODUCTION & DEFINITION

Vestibular neuronitis (VN), also termed vestibular neuritis, is an acute, benign, self-limiting inflammatory disorder of the vestibular nerve (CN VIII — vestibular division) characterised by:

A sudden onset of severe, incapacitating rotatory vertigo
Absent auditory symptoms (no hearing loss, no tinnitus)
Nausea and vomiting
Postural imbalance persisting for days to weeks

It is the second most common cause of peripheral vestibular vertigo (after BPPV), accounting for approximately 5–10% of all vestibular disorders and 3.5–9.2 per 100,000 population annually (Cummings, 7th ed.; Scott-Brown, 8th ed.).

Terminology Note: "Neuronitis" implies inflammation at the ganglion level (Scarpa's ganglion), while "neuritis" implies the nerve trunk. These terms are used interchangeably in modern literature. (Dhingra, 7th ed.)

2. ANATOMY RELEVANT TO VESTIBULAR NEURONITIS

Inner Ear Anatomy

Fig 1: Anatomical diagram and 3D FIESTA MRI showing cochlea (with scala vestibuli SV, scala tympani ST), vestibule (V), lateral (LSCC), posterior (PSCC), superior (SSCC) semicircular canals, vestibular aqueduct (VA), cochlear nerve (CN) and inferior vestibular nerve (IVN) within the internal acoustic canal (IAC).

The Vestibular Nerve — Key Anatomy

   INNER EAR
   ┌──────────────────────────────────────────┐
   │  Utricle ──┐                             │
   │  Saccule ──┤──► Superior (Utricular)     │
   │  Sup SCC ──┘    Vestibular Nerve         │
   │                        │                 │
   │  Post SCC ──► Inferior (Saccular)        │
   │  Saccule ──   Vestibular Nerve           │
   │                        │                 │
   └────────────────────────┼─────────────────┘
                            │
                     SCARPA'S GANGLION
                    (Vestibular Ganglion)
                            │
                     VESTIBULAR NERVE
                            │
                  Internal Acoustic Canal
                            │
                     BRAINSTEM
                  (Vestibular Nuclei — pons)

Key anatomical point: The superior vestibular nerve (utricular nerve) innervates the utricle, superior & lateral semicircular canals. It runs through a longer, narrower bony canal — making it more susceptible to ischemia and viral inflammation. This explains why VN predominantly affects the superior division (Hazarika, 4th ed.).

3. EPIDEMIOLOGY

Parameter	Data
Peak incidence	30–60 years
Sex	Slight male preponderance
Incidence	3.5–9.2 per 100,000/year
Proportion of vestibular vertigo	5–10%
Seasonal pattern	Spring and early summer (viral clustering)
Recurrence rate	~2% per year

(Scott-Brown 8th ed., Cummings 7th ed.)

4. ETIOLOGY & RISK FACTORS

4.1 Primary Etiology: Viral (Most Accepted)

Virus	Evidence
Herpes Simplex Virus Type 1 (HSV-1)	Most strongly implicated; HSV-1 DNA found in Scarpa's ganglion at autopsy (Arbusow et al., 1999, 2000)
Influenza virus	Epidemiological clusters
Adenovirus	Case reports
Mumps, measles	Historical reports
COVID-19 (SARS-CoV-2)	Emerging post-COVID vestibular neuritis (recent 2021–2024 literature)

4.2 Other Proposed Mechanisms

Ischemic — occlusion of the anterior vestibular artery (a terminal branch of the labyrinthine artery from AICA)
Autoimmune — post-viral immune-mediated demyelination
Vascular compression — of the vestibular nerve

Pathological Evidence (Schuknecht & Kitamura, 1981): Post-mortem studies show atrophy of the vestibular nerve, degeneration of hair cells in superior crista, and changes in Scarpa's ganglion — consistent with viral neuritis. (Quoted in Scott-Brown 8th ed., Hazarika)

5. PATHOPHYSIOLOGY

┌─────────────────────────────────────────────────────┐
│              PATHOPHYSIOLOGY FLOWCHART               │
└─────────────────────────────────────────────────────┘

  TRIGGER: Viral infection (HSV-1 reactivation) / Ischemia
                          │
                          ▼
         Inflammation / Demyelination of Vestibular Nerve
         (predominantly SUPERIOR division)
                          │
                          ▼
    ↓ Afferent Firing from AFFECTED side (e.g., Left)
                          │
              ┌──────────┴──────────┐
              │                     │
    Tonic imbalance between     VOR disruption
    Left and Right vestibular
    nuclei (Ewald's Laws)
              │                     │
              ▼                     ▼
    Pathological             Pathological
    NYSTAGMUS                 SKEW DEVIATION
    (fast phase AWAY          (ocular tilt reaction)
    from lesion side)
              │
              ▼
    Subjective VERTIGO (illusion of rotation)
    Nausea, Vomiting (vagal activation)
    Falls toward lesion side
              │
              ▼
    CNS COMPENSATION begins (days–weeks):
    - Vestibular nuclei plasticity
    - Cerebellar flocculus suppression
    - Somatosensory/visual substitution
              │
              ▼
    Gradual RESOLUTION of acute symptoms
    (Static symptoms resolve faster than dynamic)
              │
              ▼
    RESIDUAL: Chronic dizziness in 30–50% patients
    (Decompensation during stress/illness)

Ewald's Second Law Applied:

Horizontal canal ampullofugal (away from cupula) stimulation produces slower, weaker nystagmus
Loss of excitatory drive from affected side → contralateral tonic dominance → nystagmus beats TOWARD the unaffected (healthy) ear

6. CLINICAL FEATURES

6.1 Symptoms

Symptom	Description
Vertigo	Sudden onset, severe, rotatory; worst in first 24–48 hours; aggravated by head movement
Nausea & Vomiting	Severe, often intractable initially
Postural Instability	Falls/leaning toward affected side
Oscillopsia	Blurring of vision with head movement (due to VOR deficit)
Absent auditory symptoms	NO hearing loss, NO tinnitus, NO aural fullness — this is cardinal

Duration:

Acute phase: 1–3 days
Subacute imbalance: weeks to months
Complete recovery: weeks to 6 months (majority)
Chronic imbalance: 30–50% patients (Dhingra 7th ed.)

6.2 Signs on Examination

6.2.1 Nystagmus (Hallmark Sign)

Spontaneous horizontal-torsional nystagmus
Fast phase beats toward the healthy (unaffected) ear
Follows Alexander's Law: intensifies when gaze in direction of fast phase
Unidirectional — does NOT change direction with gaze (distinguishes from central)
Suppressed by visual fixation (use Frenzel glasses or VNG to unmask)

6.2.2 Head Impulse Test (HIT) — Halmagyi-Curthoys Test (Scott-Brown 8th ed.)

Positive (abnormal) HIT toward the affected side
Examiner rapidly turns head toward affected side → eyes "slip" off target → corrective catch-up saccade (overt or covert) seen
Indicates peripheral vestibular hypofunction

6.2.3 Other Signs

Sign	Finding
Romberg test	Falls toward affected side
Unterberger/Fukuda stepping test	Rotation toward affected side
Past pointing	Toward affected side
Skew deviation	Mild vertical ocular misalignment (may be present)
Dix-Hallpike	Negative (no posterior canal BPPV)

7. INVESTIGATIONS

7.1 Bedside Tests

BEDSIDE VESTIBULAR TEST BATTERY
            │
  ┌─────────┼──────────────┐
  │         │              │
HINTS   Romberg    Unterberger
Exam    Test       Test
  │
  ├── Head Impulse Test (HIT)
  ├── Nystagmus assessment (Frenzel glasses)
  └── Test of Skew (alternate cover test)

7.2 Laboratory (Audiological & Vestibular)

Test	Finding in VN	Significance
Pure Tone Audiogram (PTA)	NORMAL	Rules out labyrinthitis (hearing loss present)
Tympanometry	Normal (Type A)	Rules out middle ear pathology
Caloric Test (Bithermal)	Unilateral Canal Paresis (CP) on affected side (>25% asymmetry — Jongkees formula)	Gold standard for UVH detection
Video Head Impulse Test (vHIT)	Reduced VOR gain on affected side; corrective saccades	High-frequency canal assessment
Vestibular Evoked Myogenic Potentials (VEMPs): cVEMP	Absent on affected side if inferior nerve involved	Saccule and inferior vestibular nerve function
oVEMP	Absent on affected side if superior nerve involved	Utricle and superior vestibular nerve function
Rotatory Chair Test	Asymmetric time constants	Documents residual peripheral deficit
Posturography (CDP)	Abnormal vestibular score (condition 5 & 6)	Quantifies functional balance

Jongkees Formula for Canal Paresis (Caloric Test):

        (RW + RC) - (LW + LC)
CP% = ─────────────────────────  × 100
         RW + RC + LW + LC

Where: R = Right, L = Left, W = Warm (44°C), C = Cool (30°C)
CP > 25% = Significant Unilateral Canal Paresis (UCP)

(Cummings 7th ed., p. 2720; Dhingra 7th ed.)

7.3 Imaging

Modality	Indication	Findings
MRI Brain with Gadolinium (FLAIR + DWI)	To exclude central causes (stroke, MS, tumor)	Enhancement of vestibular nerve (acute VN); Normal in majority
3D FIESTA / CISS MRI	Detailed IAC and nerve assessment	Nerve atrophy in chronic VN
CT Temporal Bone	If associated trauma/OM suspected	Usually normal
MRI DWI	Acute — must rule out cerebellar/lateral medullary infarct	Normal in VN

When to image (RED FLAGS):

HINTS exam suggests central cause
Neurological signs present
Risk factors for stroke (age >60, hypertension, diabetes, AF)

8. HINTS EXAM (Key Bedside Algorithm)

The HINTS battery (Head Impulse, Nystagmus, Test of Skew) is more sensitive than early MRI-DWI for ruling out posterior fossa stroke (Kattah et al., Stroke 2009; Scott-Brown 8th ed.)

┌──────────────────────────────────────────────────────────────┐
│                    HINTS EXAM ALGORITHM                      │
└──────────────────────────────────────────────────────────────┘

                    Acute Vestibular Syndrome
                           │
              ┌────────────┼────────────┐
              │            │            │
         Head Impulse   Nystagmus   Test of Skew
           (HIT)       Direction    (Alternate
                                   Cover Test)
              │            │            │
              │            │            │
    ┌─────────┴──┐  ┌──────┴───┐  ┌─────┴──────┐
    │  Positive  │  │Unidirec- │  │  Absent    │
    │  (catch-up │  │tional,   │  │  Skew      │
    │  saccade)  │  │Horizontal│  │ Deviation  │
    └────────────┘  └──────────┘  └────────────┘
              │            │            │
              └────────────┴────────────┘
                           │
                    ┌──────┴──────┐
                    │  ALL THREE  │
                    │  PERIPHERAL │
                    │  FEATURES   │
                    └──────┬──────┘
                           │
                  PERIPHERAL CAUSE
               (Vestibular Neuronitis)
                   Low stroke risk

  IF ANY ONE IS "CENTRAL" (HIT negative + direction-changing
  nystagmus + present skew) → CENTRAL CAUSE → URGENT MRI

Feature	Peripheral (VN)	Central (Stroke/MS)
HIT	Positive (catch-up saccade)	Negative (normal)
Nystagmus	Unidirectional, horizontal-torsional	Direction-changing or purely vertical
Skew	Absent	Present
Hearing	Normal	May be abnormal
Neurological signs	Absent	Present

9. DIAGNOSIS

9.1 Diagnostic Criteria (Dhingra, Hazarika)

Diagnosis is CLINICAL:

Acute onset severe vertigo
Nausea and vomiting
No auditory symptoms (no hearing loss, no tinnitus)
Spontaneous horizontal-torsional nystagmus toward healthy ear
Positive HIT toward affected side
Unilateral canal paresis on caloric testing
No neurological signs

9.2 Caloric Test Patterns

NORMAL:                    VESTIBULAR NEURONITIS:
Left ear       Right ear   Left ear (affected)  Right ear
  ██████           ██████    ██ (reduced)           ██████
  Warm=30          Warm=30   Warm=5                 Warm=30
  Cool=20          Cool=20   Cool=3                 Cool=20

                            Canal Paresis LEFT > 25%

10. DIFFERENTIAL DIAGNOSIS

                ACUTE SEVERE VERTIGO
                        │
        ┌───────────────┼───────────────┐
        │               │               │
   PERIPHERAL       CENTRAL        SYSTEMIC
     CAUSES          CAUSES          CAUSES
        │               │               │
  ┌─────┴─────┐   ┌─────┴─────┐   ┌────┴────┐
  Vestibular   │   Cerebellar  │   Drug     │
  Neuronitis   │   infarct     │   toxicity │
               │               │            │
  BPPV         │   Lateral     │   Cardiac  │
  (positional) │   medullary   │   arrhythmia│
               │   syndrome    │            │
  Labyrinthitis│   (Wallenberg)│   Ortho-   │
  (+ deafness) │               │   static   │
               │   MS plaque   │            │
  Meniere's    │               │   Anemia   │
  (+ deafness  │   AICA        │            │
   + tinnitus) │   stroke      │   Anxiety/ │
               │               │   Panic    │
  Perilymph    │   Tumor        │            │
  fistula      │   (acoustic)  │            │
  └────────────┘  └────────────┘  └──────────┘

Differentiating Key Conditions

Feature	Vestibular Neuronitis	Labyrinthitis	BPPV	Menière's Disease
Vertigo	Persistent, severe, acute	Persistent, severe	Positional, brief (<1 min)	Episodic (20 min–hours)
Hearing loss	Absent	Present	Absent	Present (fluctuating)
Tinnitus	Absent	May be present	Absent	Present
Nausea/Vomiting	Severe	Severe	Mild–moderate	Moderate
Caloric test	UCP affected side	UCP affected side	Normal	UCP affected side
Dix-Hallpike	Negative	Negative	Positive	Negative
Duration	Days (acute), weeks (imbalance)	Days–weeks	Seconds	20 min – 24 hours
Preceding URTI	Common	Common	No	No

(Stell & Maran; Cummings 7th ed.)

11. MANAGEMENT

11.1 Management Flowchart

┌──────────────────────────────────────────────────────────────┐
│            VESTIBULAR NEURONITIS — MANAGEMENT                │
└──────────────────────────────────────────────────────────────┘

PATIENT PRESENTS WITH ACUTE SEVERE VERTIGO
                    │
                    ▼
          CLINICAL ASSESSMENT
          + HINTS EXAM + PTA
                    │
          ┌─────────┴──────────┐
          │                    │
   PERIPHERAL signs       CENTRAL signs
   (VN likely)            (Stroke/MS)
          │                    │
          ▼                    ▼
   TREAT AS VN          URGENT MRI
                        Neurology referral
          │
          ▼
    ACUTE PHASE                      RECOVERY PHASE
   (Days 1–3)                        (Day 4 onwards)
          │                                  │
  ┌───────┴──────┐                  ┌────────┴───────┐
  │              │                  │                │
VESTIBULAR   CORTICO-          VESTIBULAR      VESTIBULAR
SUPPRESSANTS  STEROIDS         REHABILI-       SEDATIVES
  +           (Methyl-         TATION          TAPER OFF
ANTIEMETICS   prednisolone)    EXERCISES       (critical)

11.2 Acute Phase Pharmacotherapy (Days 1–5)

A. Vestibular Suppressants / Antiemetics

Drug	Class	Dose	Route	Notes
Prochlorperazine	Phenothiazine (D2 blocker)	5–10 mg TDS	PO / IM	First line antiemetic
Promethazine	H1 antihistamine	25 mg Q6h	PO / IM	Sedating; useful at night
Cinnarizine	H1 blocker + Ca²⁺ blocker	25–75 mg TDS	PO	Widely used in India (Zakir Hussain, Dhingra)
Betahistine	H3 antagonist / H1 agonist	24 mg BD	PO	Improves labyrinthine microcirculation; used in recovery
Diazepam	Benzodiazepine	5–10 mg	PO / IV	Acute crisis only; SHORT term
Ondansetron	5-HT3 antagonist	4–8 mg BD	PO / IV	Refractory vomiting
Metoclopramide	D2 antagonist	10 mg TDS	PO / IV	Central and peripheral antiemetic

⚠️ CRITICAL PRINCIPLE: Vestibular suppressants must be STOPPED after 3–5 days to allow and not impede CNS compensation (vestibular rehabilitation). Prolonged use delays recovery. (Hazarika; Scott-Brown 8th ed.)

B. Corticosteroids (Disease-Modifying)

Drug	Protocol	Evidence
Methylprednisolone	100 mg/day tapering over 3 weeks	Strupp et al., NEJM 2004: improved caloric recovery at 12 months
Prednisolone	1 mg/kg/day × 5 days then taper	Alternative regimen

Evidence Base: The landmark Strupp et al. (NEJM, 2004) RCT showed methylprednisolone significantly improved peripheral vestibular function at 12 months vs. placebo. Valaciclovir (antiviral) alone was NOT superior to placebo.

RGUHS Exam Point: Steroids improve the peripheral vestibular function recovery but do NOT significantly affect subjective dizziness outcomes in all studies.

C. Antivirals — Controversial

Antiviral	Status	Evidence
Acyclovir / Valaciclovir	NOT recommended routinely	Strupp 2004: no benefit over placebo for caloric recovery
Combination (steroid + antiviral)	No added benefit shown	(Fishman et al., Cochrane 2011)

11.3 Vestibular Rehabilitation (VR) — Cornerstone of Recovery

The most important long-term treatment (Scott-Brown 8th ed.; Cummings 7th ed.)

VESTIBULAR REHABILITATION EXERCISES
               │
    ┌──────────┼─────────────┐
    │          │             │
BRANDT &   CAWTHORNE-    GAZE
DAROFF     COOKSEY       STABILIZATION
EXERCISES  EXERCISES     EXERCISES
    │          │             │
Habituation  Progressive  VOR × 1, × 2
exercises   head/eye     cancellation
(supine →   movements    exercises
 sitting →  (bed → chair
 standing)  → standing
            → walking)

Cawthorne-Cooksey Exercises (in bed → standing → walking)

Phase 1 — In Bed:

Eye movements — up/down, side to side, focusing on moving finger
Head movements — slowly then quickly (eyes open then closed)

Phase 2 — Sitting:

Eye and head movements as above
Shoulder shrugging and circling
Bending forward to pick up objects

Phase 3 — Standing:

Above eye, head, shoulder exercises
Changing from sitting to standing with eyes open/closed
Throwing ball hand-to-hand

Phase 4 — Moving About:

Walking across the room, up/down slopes, stairs
Games requiring bending and stretching

11.4 Surgical Treatment

No surgical intervention is required for VN. However, for chronic, intractable cases:

Vestibular nerve section (rarely) — if debilitating recurrent vertigo and failed all conservative treatment
Chemical labyrinthectomy (intratympanic gentamicin) — only if combined with labyrinthine disease

12. PATTERN OF NERVE INVOLVEMENT (Superior vs. Inferior VN)

Type	Affected Division	Structures Involved	VEMPs
Superior VN (most common, ~85%)	Superior vestibular nerve	Utricle, Horizontal & Superior SCC	Abnormal oVEMP; Normal cVEMP
Inferior VN (~15%)	Inferior vestibular nerve	Saccule, Posterior SCC	Normal oVEMP; Abnormal cVEMP
Complete VN	Both divisions	All end organs	Both oVEMP & cVEMP abnormal

(Recent literature: Kim & Kim, 2012; Magliulo et al.; Scott-Brown 8th ed.)

13. PROGNOSIS

Outcome	Percentage	Timeline
Complete subjective recovery	~50%	Within 6 months
Good functional recovery	~95%	Within 1 year
Persistent mild dizziness	~30–50%	Long-term
Development of BPPV post-VN	~15%	Post-acute phase
Recurrence of VN	~2%/year	Long-term follow-up

Prognostic Factors:

Younger age → better recovery
Early vestibular rehabilitation → faster compensation
Early steroid treatment → better caloric recovery (Strupp 2004)
Severe initial caloric canal paresis → slower recovery
Psychological factors (anxiety, depression) → worse outcome

(Hazarika, Cummings 7th ed.)

14. COMPLICATIONS

Persistent Vestibular Hypofunction — chronic imbalance, oscillopsia
Secondary BPPV — canaliths from utricular degeneration enter posterior canal (~15%)
Phobic Postural Vertigo — psychological overlay (chronic anxiety-related dizziness)
Chronic Subjective Dizziness (CSD) / Persistent Postural-Perceptual Dizziness (PPPD) — newer classification
Falls and Injury — particularly in elderly
Vestibular Migraine — may be unmasked

15. RECENT ADVANCES (2018–2024)

15.1 Diagnostic Advances

Advance	Details
Video Head Impulse Test (vHIT)	High-frequency canal function; detects covert saccades missed by clinical HIT; canal-specific diagnosis
MRI with Gadolinium (3T/7T)	Gadolinium enhancement of vestibular nerve in acute phase confirms diagnosis
oVEMP and cVEMP panel	Superior vs. inferior VN differentiation; prognostic value
HINTS Plus	Addition of audiogram (HINTS+) improves sensitivity for central detection
Smartphone-based nystagmography	Low-cost HIT recording using phone camera apps

15.2 Pathophysiological Advances

HSV-1 latency in Scarpa's ganglion confirmed by multiple post-mortem and molecular studies — strongest evidence for viral etiology
Superior vestibular artery anatomy explains predilection for superior division — narrower bony canal, terminal vasculature
Neuroinflammation markers — elevated IL-6, TNF-α found in some VN patients
Post-COVID Vestibular Neuritis (2021–2024): multiple case series report acute VN following COVID-19 infection / vaccination, possibly via spike-protein-mediated inflammation of CN VIII

15.3 Treatment Advances

Advance	Status
VR via Telemedicine / Mobile Apps (e.g., VRT apps)	Validated in RCTs 2020–2023; non-inferior to supervised VR
rTMS (repetitive Transcranial Magnetic Stimulation)	Experimental; modulates vestibular cortex adaptation
Neurofeedback and VR (Virtual Reality) rehabilitation	Immersive VR balance training — promising pilot studies
Intranasal antivirals	Under investigation for direct cochlear/vestibular nerve delivery
Optimal steroid regimen	Ongoing debate; some favour intratympanic route
PPPD treatment (SSRIs + VR)	Established for chronic phase; Fluoxetine/Venlafaxine + VR exercise

15.4 Classification Update

Bárány Society Diagnostic Criteria for Vestibular Neuritis (2022):
- Acute vestibular syndrome
- Pathological HIT
- No auditory or neurological symptoms
- Absence of central signs on HINTS
- Unilateral vestibular hypofunction on caloric/vHIT

16. COMPLETE MANAGEMENT SUMMARY FLOWCHART

┌──────────────────────────────────────────────────────────────┐
│        VESTIBULAR NEURONITIS — COMPLETE ALGORITHM            │
└──────────────────────────────────────────────────────────────┘

          ACUTE VERTIGO + NAUSEA/VOMITING
                       │
                 HISTORY & EXAM
                       │
         ┌─────────────┼─────────────┐
         │             │             │
    HINTS EXAM       PTA          NEUROLOGY
    (HIT + Nyst.   (Hearing        SCREEN
    + Skew)         Normal?)
         │
    ALL PERIPHERAL?
    ┌────┴────┐
   YES        NO
    │          │
    ▼          ▼
VESTIBULAR  URGENT MRI
NEURONITIS  + NEUROLOGY
CONFIRMED   REFERRAL
    │
    ├──────────────────────────────┐
    │                              │
 ACUTE (Day 1–3)           RECOVERY (Day 4+)
    │                              │
 Admit (if severe)          STOP VESTIBULAR
 IV fluids                  SUPPRESSANTS
 Prochlorperazine          │
 Cinnarizine               ├─ VESTIBULAR REHAB
 Methylprednisolone            (Cawthorne-Cooksey)
 (100mg → taper 3/52)     │
                           ├─ Betahistine 24mg BD
                           │   (optional)
                           │
                           ├─ FOLLOW UP 4/52
                           │  (Caloric / vHIT)
                           │
                           └─ IF BPPV develops
                              → Epley Manoeuvre

17. TABULAR SUMMARY FOR QUICK REVISION

Aspect	Key Points
Definition	Acute inflammation of vestibular nerve; no hearing loss
Etiology	HSV-1 reactivation (most accepted); viral, ischemic, autoimmune
Pathology	Schuknecht: atrophy of vestibular nerve, Scarpa's ganglion changes
Predominant division	Superior vestibular nerve (85%)
Key symptom	Sudden severe rotatory vertigo, no deafness
Key sign	Horizontal-torsional nystagmus (fast phase to healthy side)
Bedside test	HIT positive (catch-up saccade toward affected side)
Caloric	Unilateral canal paresis (affected side, >25%)
Distinguish central	HINTS exam (HIT +ve / Unidirectional Nystagmus / No Skew = Peripheral)
Acute treatment	Prochlorperazine, Cinnarizine, Methylprednisolone
Long-term treatment	Vestibular rehabilitation (Cawthorne-Cooksey)
Landmark study	Strupp et al., NEJM 2004 — steroids improve caloric recovery
Prognosis	Mostly good; 30–50% mild residual symptoms
Complication	Secondary BPPV (15%); PPPD
Recent advance	vHIT, superior vs. inferior VN classification, Post-COVID VN, VR rehab

REFERENCES

Scott-Brown's Otorhinolaryngology, Head & Neck Surgery (8th ed., 2018) — Vol 3, Otology, Chapter on Peripheral Vestibular Disorders
Cummings Otolaryngology: Head and Neck Surgery (7th ed., 2021) — Chapter 165: Peripheral Vestibular Disorders
Stell and Maran's Textbook of Head & Neck Surgery and Oncology (5th ed.) — Vestibular Disorders
Dhingra PL & Dhingra S — Diseases of Ear, Nose & Throat (7th ed., 2018) — Chapter: Vestibular Neuronitis
Hazarika P et al. — Textbook of Ear, Nose and Throat Diseases (12th ed.) — Vertigo and Vestibular Disorders
Zakir Hussain — Textbook of ENT & Head-Neck Surgery — Vestibular Disorders
Strupp M, Zingler VC, Arbusow V, et al. — "Methylprednisolone, Valacyclovir, or the Combination for Vestibular Neuritis." NEJM 2004; 351:354–361
Schuknecht HF, Kitamura K. Vestibular neuritis. Ann Otol Rhinol Laryngol Suppl. 1981;90(1 Pt 2):1-19
Kattah JC et al. — "HINTS to Diagnose Stroke in the Acute Vestibular Syndrome." Stroke 2009; 40:3504–3510
Arbusow V et al. — "HSV-1 not only in human vestibular ganglia but also in the vestibular labyrinth." Audiol Neurootol. 2001
Kim JS, Kim HJ — "Inferior vestibular neuritis." J Neurol. 2012
Bárány Society Diagnostic Criteria for Vestibular Neuritis — J Vestib Res. 2022
Post-COVID Vestibular Neuritis — Multiple case series 2021–2024, JAMA Otolaryngology, Otol Neurotol

RGUHS Exam Tip (50 Marks): For a 50-mark answer, include: Introduction + Anatomy (5 marks) → Etiology + Pathophysiology (8 marks) → Clinical features + Signs (8 marks) → Investigations with caloric formula (8 marks) → Differential diagnosis table (5 marks) → HINTS exam (4 marks) → Management with drug table and VR (8 marks) → Complications + Prognosis (2 marks) → Recent advances (2 marks). Draw at minimum: ① Anatomical diagram of vestibular nerve pathway, ② Pathophysiology flowchart, ③ HINTS algorithm, ④ Management flowchart.

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