Nexus Letter for Traumatic Brain Injury: What It Must Say
The medical opinion connecting Traumatic Brain Injury (8045) to your service is the piece of the file a rater weighs most heavily. This is what that letter has to contain — and a complete, real example you can read before writing a word.
What a nexus letter is
A nexus letter is a written medical opinion from a licensed clinician stating that a veteran’s condition is “at least as likely as not” (a 50 percent or greater probability) connected to their military service — or to a condition already service-connected. It is the bridge between a diagnosis and service connection: the VA has your diagnosis and your service records, and the nexus opinion is what ties them together with medical reasoning a rater can weigh.
What a Traumatic Brain Injury nexus letter must contain
The diagnosis, by name and code
Traumatic Brain Injury named as a current, documented diagnosis — the condition the VA rates under 38 CFR Part 4, DC 8045 (8045). No diagnosis, no service connection: the opinion has to be about a condition that exists in your records.
The theory of connection
For most Traumatic Brain Injury claims this is direct service connection under 38 C.F.R. § 3.303 — the letter connects the condition to an in-service event, injury, or exposure, and says so explicitly.
The magic words, used correctly
The opinion must be stated to the VA's own standard: "at least as likely as not (a 50 percent or greater probability)." Weaker hedges like "possibly" or "may be related" fail; the standard is a specific legal threshold, and letters that don't invoke it get discounted.
A rationale, not a conclusion
The most common fatal flaw is the conclusory letter — an opinion with no reasoning. A rater is instructed to weigh the rationale: what in the records supports the connection, what the medical literature says about the mechanism, and why known alternative causes don't displace it. For Traumatic Brain Injury specifically: Documentation of the in-service head injury (the event, and any loss of consciousness or altered awareness) plus a TBI/neuro-psych evaluation that describes each facet in the table’s own terms — objective testing where it exists, and the day-to-day residuals (memory, judgment, mood, headaches, dizziness, sleep) in frequency and severity. Migraines, a mental-health condition, or other residuals with their own code are rated separately on top of this.
A licensed clinician's signature and credentials
The letter is medical evidence only when a licensed clinician — opining within their specialty — reviews it, exercises independent judgment, and signs it with their credentials. VA Claim Commander drafts the letter from your records and your story; your clinician signs it. An unsigned draft is a draft.
Why nexus letters fail
- Conclusory: an opinion with no rationale. The rater is told to weigh reasoning, and a bare “it’s related” weighs nothing.
- Wrong standard: “may be related” or “possibly caused by” instead of “at least as likely as not.”
- Ignores the other causes: a strong letter names the recognized non-service risk factors and explains why they don’t displace the service connection.
- Outside the specialty: a clinician opining far from their field gets less weight than one whose practice covers the condition.
- Unsigned: a draft nobody signed is not medical evidence — it is homework.
Read a complete nexus letter — free, no account
4,348 words, 11 verified studies, the § 3.310 secondary framework — published in full so you can see the standard before you write a word.
Drafts are prepared for review and signature by a licensed clinician. Documentation quality is the promise — never a claim outcome.
Common questions
Do I need a nexus letter for a Traumatic Brain Injury VA claim?
If service connection isn't already established for Traumatic Brain Injury, a medical nexus opinion is usually the piece a rater weighs most heavily. It connects the diagnosis (8045) to your service — or to an already service-connected condition — using the "at least as likely as not" standard. Presumptive claims are the main exception.
What must a nexus letter for Traumatic Brain Injury say?
Four things: the current diagnosis by name and diagnostic code; the connection theory (direct under 38 C.F.R. § 3.303, or secondary under § 3.310); the opinion stated to the "at least as likely as not (50 percent or greater probability)" standard; and a medical rationale grounded in your records and the medical literature — not a bare conclusion. It must be signed by a licensed clinician.
Who has to sign a nexus letter?
A licensed medical professional — a physician, or another clinician opining within their specialty. VA Claim Commander drafts the letter from your own records and story; a licensed clinician reviews, exercises independent judgment, and signs. An unsigned draft is not medical evidence.