New developments to progress diagnostic criteria for Mild Traumatic Brain Injury (TBI) are discussed by The Mild Traumatic Brain Injury (TBI) Task Force of the American Congress of Rehabilitation Medicine Brain Injury Special Interest Group.
In May of 2023, the Mild Traumatic Brain Injury (TBI) Task Force of the American Congress of Rehabilitation Medicine Brain Injury Special Interest Group convened to develop an evidence review of and expert consensus process for new diagnostic criteria for mild TBI, which was published last month. A mild TBI can occur when an external force causes a rapid acceleration or deceleration of the brain within the skull. This linear, translational, or rotational force placed on the brain then leads to a complex pathophysiological process that results in a physiological disturbance in brain function. The patient must have a one or more clinical signs and at least two acute symptoms and at least one clinical or laboratory finding attributable to the brain injury.1
A common symptom in mild TBI is double vision, which is most commonly due to convergence insufficiency (CI) or pseudo-convergence insufficiency due to an underlying accommodative insufficiency.2 Thus, a patient with diplopia post-concussion should complain of intermittent horizontal diplopia with or without blurry vision at near, that is worse with prolonged near tasks like computer or reading and is alleviated by taking breaks and looking far away. Diplopia that is vertical, constant, at distance, or gaze related is atypical (but not impossible) for a mild TBI and should have a comprehensive neurologic/ophthalmologic/neuro-optometric workup.
Unlike the typical developmental CI as defined by the CITT trial,3 post-traumatic convergence deficits may not have all of the developmental CI criterion including exophoria larger at near than at distance or reduced fusional convergence.4 For example, some patients may have an esophoria with a reduced near point of convergence (NPC), a finding atypical in the developmental population. Additionally, testing may provoke immediate and intense symptoms like headache, dizziness, nausea, and brain fog.5 If a patient is voicing post-concussion diplopia complaints—providers should perform cover test at distance and near, NPC, and monocular near point of accommodation (NPA) testing at minimum. Since patients often fatigue over time, it is important to repeat the NPC and NPA testing 3-5 times as many patients go undiagnosed because their initial performance is within norms.Providers should also note symptom provocation with testing and if not performing a comprehensive oculomotor evaluation, perform a screening vestibular-oculomotor assessment like the VOMS and triage to a tertiary care neuro-optometrist as indicated.
Interestingly, oculomotor/diplopia deficits may not manifest at the time of injury, but rather may develop over the next few hours or days.6 The majority of patients post-concussion ~75%, will have vestibular-oculomotor complaints acutely, and the majority of those patients will self-resolve within 3-4 weeks.7 If seeing the patient acutely (<1 week from injury), a practitioner can start active vision rehab depending on how the patient is feeling, or depending on their practice/the patient, they can wait to refer only those with persistent post-concussion symptoms that are 4 weeks post-injury for active vision therapy to alleviate the patient’s oculomotor complaints.8,9