Nexus Letter for Vertigo Secondary to TBI (2026)

The Secondary Pathway: TBI to Vertigo

Under 38 CFR 3.310, a condition that is proximately caused or aggravated by a service-connected disability is eligible for secondary service connection. Traumatic brain injury (TBI) is one of the most heavily documented causes of post-traumatic vertigo in the medical literature. The pathway is recognized in the published guidance, in published clinical research, and in standard textbooks of otology and neuro-otology.

TBI is a common service-connected condition for veterans, particularly those who served in combat, were exposed to blast, or experienced motor vehicle or training-related head impacts. Once TBI is service-connected, vertigo that arose with or after the TBI sits squarely on the secondary service-connection pathway when the medical evidence supports the connection.

The Three Mechanisms

A defensible nexus letter benefits from identifying which of the three principal mechanisms best fits the clinical picture. In many cases more than one mechanism is at play; the letter should name the dominant pathway and acknowledge contributing mechanisms.

1. Central Vestibular Dysfunction

The central vestibular system includes brainstem nuclei, cerebellar pathways, and cortical processing centers. TBI involving shear injury to white matter tracts, brainstem contusion, or cerebellar contusion produces central vestibular dysfunction. Symptoms typically include persistent unsteadiness, gait imbalance, and dizziness that worsens with visual motion. Central vertigo often produces nystagmus that is non-fatigable, gaze-direction-changing, or vertical, distinguishing it from peripheral vertigo.

2. Peripheral Vestibular Injury

Peripheral vestibular injury involves the inner ear structures (the semicircular canals, otolith organs, and the vestibular nerve itself). Common mechanisms after TBI include labyrinthine concussion (microhemorrhage or membrane disruption inside the labyrinth), temporal bone fracture transecting or compressing the vestibular nerve, and perilymph fistula from sudden pressure changes during the injury. Peripheral vertigo is typically episodic, severe, and accompanied by horizontal-rotary nystagmus that fatigues with repetition.

3. Post-Traumatic BPPV

Benign paroxysmal positional vertigo (BPPV) is the most common type of post-traumatic vertigo. The mechanism is dislodgement of otoconia (calcium carbonate crystals) from the utricle into one of the semicircular canals at the moment of head impact. The displaced crystals create position-triggered vertigo when the patient moves the head in certain directions, classically when rolling over in bed, looking up, or bending forward. Post-traumatic BPPV is bilateral or atypical more often than idiopathic BPPV. Diagnosis is by Dix-Hallpike maneuver (posterior canal BPPV) or roll test (horizontal canal BPPV).

Rating Framework (DC 6204 and DC 8045)

DC 6204 — Peripheral Vestibular Disorders

Under 38 CFR 4.87, peripheral vestibular disorders are rated under DC 6204 with two tiers:

• 30% — Dizziness and occasional staggering.
• 10% — Occasional dizziness.

A note under DC 6204 states that hearing impairment and suppuration are to be evaluated separately under the appropriate diagnostic codes, indicating that the rater views vestibular impairment as functionally distinct from other ear residuals.

DC 8045 — Residuals of TBI

Under 38 CFR 4.124a, the residuals of TBI are evaluated under DC 8045 using a facet-based table covering ten domains: memory/attention/concentration/executive functions, judgment, social interaction, orientation, motor activity, visual spatial orientation, subjective symptoms, neurobehavioral effects, communication, and consciousness. Each facet receives a level from 0 to 3 or "total." Total residual rating is determined by the highest single facet level, with a 40% rating for the highest level 2 facet, a 70% rating for the highest level 3 facet, and 100% for total.

Vertigo and dizziness are part of the "subjective symptoms" facet under DC 8045, with severity calibrated by the impact of the symptom complex on daily life.

How the Two Codes Interact

The general rule under 38 CFR 4.14 is that the same impairment cannot be rated twice (the prohibition on pyramiding). When vertigo is part of the TBI residual symptom complex, it is generally rated under DC 8045 as part of the "subjective symptoms" facet rather than separately under DC 6204. However, when the vertigo arises from a distinct anatomical mechanism (e.g., peripheral labyrinthine injury producing classic BPPV) that is separable from the broader TBI residuals, separate evaluation under DC 6204 may be appropriate when the medical evidence supports the separation.

A well-constructed nexus letter helps the VA see whether the vertigo is best framed as a TBI residual or as a separable peripheral vestibular disorder. The choice has real rating consequences.

What a Strong Nexus Letter Must Include

Identification of the Service-Connected TBI

The letter must reference the rating decision or VA record that established service connection for the TBI, the date of injury, and the documented mechanism (blast, blunt impact, motor vehicle, fall).

Severity of the TBI

VA classifies TBI as mild, moderate, or severe based on duration of loss of consciousness, post-traumatic amnesia, alteration of consciousness, and imaging findings. Severity matters because mild TBI typically produces peripheral or BPPV-type vertigo, while moderate to severe TBI more often involves central vestibular dysfunction.

Mechanism Identification

The letter should identify which of the three mechanisms (central, peripheral, BPPV) best explains the veteran's vertigo and explain why. This is where the medical rationale lives. Cite the relevant clinical findings: nystagmus pattern, Dix-Hallpike result, VNG or ENG results if available, audiology data, imaging.

Temporal Relationship

Document when vertigo first appeared in relation to the TBI. Onset within days to months is consistent with all three mechanisms. Onset years later requires more careful explanation, often with reference to delayed-presentation patterns documented in the literature.

Differential Considerations

A thorough letter briefly addresses alternative causes: vestibular migraine, Meniere disease, vestibular neuritis, medication side effects, orthostatic hypotension. Explain why these are insufficient to outweigh the TBI contribution.

The Required Legal Standard

The opinion must use "at least as likely as not" to indicate that the probability of causation or aggravation is 50% or greater. Language such as "could be," "may have contributed," or "possibly related" does not satisfy the VA's evidentiary threshold.

Records-Based Review Statement

The letter must affirm review of the veteran's service treatment records, VA records, neurology and otology consultations, audiology, imaging, and any private medical documentation. A records-based opinion carries substantially more weight than an opinion written without records review.

Supporting Evidence

• Rating decision or VA letter establishing service connection for TBI, including documented severity classification.
• Service treatment records documenting the TBI event (loss of consciousness, post-traumatic amnesia, GCS score, imaging at time of injury).
• Neurology consultation notes documenting cranial nerve exam, gait, Romberg, and oculomotor findings.
• Otology / neuro-otology consultation with VNG, ENG, or videonystagmography results if available.
• Audiology testing showing any associated sensorineural hearing loss (often co-occurring with peripheral vestibular injury).
• Imaging — CT temporal bones, MRI brain and internal auditory canals.
• Dix-Hallpike and roll test documentation if BPPV is suspected.
• Treatment records for vestibular rehabilitation, Epley maneuvers, vestibular suppressants, anti-emetics.
• Symptom log or functional impact statement documenting frequency, triggers, and impact on driving, work, and daily activities.

Differential Considerations

A complete nexus letter addresses the most common alternative explanations for vertigo and explains why they do not outweigh the TBI mechanism:

• Vestibular migraine — Often co-exists with TBI. Address with reference to migraine history and headache patterns.
• Meniere disease — Distinguished by the classic triad of episodic vertigo, fluctuating hearing loss, and tinnitus, plus aural fullness.
• Vestibular neuritis — Single severe vertigo episode with viral prodrome, typically resolves over weeks.
• Medication side effects — Common offenders include certain antihypertensives, antidepressants, anticonvulsants, and aminoglycoside antibiotics.
• Orthostatic hypotension — Distinguished by timing with postural change and resolution with sitting.
• Cervicogenic dizziness — Distinguished by reproduction with cervical motion and association with neck pain.

Common Mistakes

• Treating "vertigo" as a single phenomenon. The three mechanism categories require different clinical findings and produce different rating outcomes.
• Missing the temporal anchor. A nexus letter that does not specify when vertigo first appeared relative to the TBI cannot establish the secondary connection cleanly.
• Not addressing the central vs peripheral question. Raters and reviewers look for this distinction. A letter that does not engage with it appears clinically thin.
• Pyramiding risk. Claiming both DC 8045 and DC 6204 for the same impairment without a separable anatomical basis is rejected under 38 CFR 4.14.
• Wrong legal standard. Letters using "possibly," "could be," or "may be" fall below the "at least as likely as not" threshold.
• No records review. An opinion written without reviewing service treatment records, neurology and otology consultations, and imaging is given reduced evidentiary weight.
• Ignoring aggravation. Even if the veteran had pre-existing vertigo or a mild vestibular condition before service, aggravation by an in-service TBI is a valid secondary pathway when properly documented.