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Medical Nexus Definition

In order for any VA disability claim for service connection to be successful, three main elements must be present. Specifically, to establish service connection on a direct basis, veterans must show evidence of:

  • A current, diagnosed condition
  • An in-service event, injury, or illness; and
  • A medical nexus between the current condition and the in-service event, injury, or illness

Providing a medical nexus is often the most difficult part of this process, as it ties a veteran’s claim for service connection together. Sometimes, VA will schedule veterans for a Compensation & Pension (C&P) examination in order for a VA examiner to determine if there is a link between their condition and their military service. However, a veteran can fulfill this requirement by having a medical professional write a nexus letter for their claim.

In either case, the language the treating physician uses when providing a medical nexus is critical. Unlike other areas of the law, VA has a unique evidentiary standard, or “standard of proof,” when it looks at veterans’ claims for disability benefits. The standard often referred to equipoise or the tie goes to runner is framed in the following terms:“at least as likely as not”. If the issue is service connection for a back condition, then the doctor’s letter should state that “it is at least as likely as not that the veteran’s back condition is due to her service”. This “at least as likely as not language” sets forth the proper standard for proving service connection. Therefore, it is very important for veterans to make sure medical nexus letters and opinions use this language as it is what VA looks for when adjudicating claims for service connection.

When is a Medical Nexus Not Required?

In some cases, a medical nexus is not required in order to establish service connection. This occurs when there is already a presumption of service connection. Generally speaking, a presumption of service connection is when VA presumes a veteran’s condition was caused by their military service, usually due to a certain exposures. The presumption of service connection takes the place of the medical nexus requirement in obtaining service connection. In other words, the presumption acts as the link between the veteran’s military service and their current condition. VA has several presumptions that apply to different groups of veterans based on what they were exposed to during their military service.