Dizziness is a common complaint after brain injury. When doctors hear, “I feel dizzy,” there is an immediate assumption of a vestibular system problem.
However, patients may use the word “dizzy” to refer to a variety of symptoms, many of which have visual causes. It is worthwhile to dig a little deeper into what they mean by dizzy.
The sensation that the person or room is spinning is almost always due to vestibular causes, although an upper cervical injury, such as in whiplash, may also contribute to this symptom. Cervical vertigo is unrelated to head position and may respond to osteopathic or nonmanual chiropractic treatment.
On the other hand, visual midline shift syndrome after brain injury can give patients a feeling of dizziness because their perception of what is straight ahead in space is out of sync with reality. Patients with this condition feel disoriented and off balance, which they frequently describe as feeling dizzy. They often lean or veer in one direction when walking. In such cases, vestibular therapy won’t help at all, while yoked prism glasses that match the patient’s perception of straight ahead with true physical straight ahead, can provide marked and immediate symptom relief.
Subtle vertical phorias, or misalignments, are also very common after brain injury. In a neurotypical individual, the ocular superior and inferior recti and oblique muscles that control vertical alignment are constantly working together to keep both eyes at the same vertical position as the direction of gaze shifts. But after a brain injury, subtle cranial nerve palsies or skew deviations may lead to vertical misalignments. It won’t be as immediately apparent as true strabismus, and the misalignment often doesn’t occur in all directions of gaze, so the brain has difficulty compensating for the misalignment as gaze is shifted. This can lead patients to suddenly feel unstable, as if the floor shifted when they shifted their gaze, and may be perceived as dizziness.
Fortunately, there are some quick screening tools to help you determine whether patients are suffering from visual or vestibular problems, so you can make a better referral for the next step in their care.
A careful query regarding the nature of the dizziness and when it occurs is helpful. Another helpful method is the head shake test. Tilt the patient’s head forward approximately 15 degrees. Then, have them shake their head “no” (laterally) for 10 to 15 seconds at approximately one cycle/second. Induced nystagmus can be observed in the biomicroscope at cessation of head turning. Alternatively, if you have the patient read the lowest line they are able to read on a nearpoint acuity card and then shake their head, induced nystagmus will temporarily degrade their visual acuity after cessation of head shaking. If the visual acuity is unaffected after cessation of head movements, the problem is most likely a visual one.
To evaluate subtle vertical phorias, check the vertical phoria with a Maddox rod test in at least the lower six fields of gaze while seated upright If you find a vertical phoria, repeat this with the patient supine. If the phoria disappears when supine, the vestibular system is involved in creating the misalignment, and the patient has a “skew deviation.” These patients should be referred for both vestibular and visual system workup and treatment.
For visual system dysfunction, refer to a neuro-optometrist. Vestibular problems can be referred to a neuro-otologist (sometimes hard to find) or a vestibular rehabilitation therapist, who may work for an ear, nose and throat specialist or at a concussion care clinic.
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Penelope Suter, OD, FCOVD, FNORA, is in private practice in Bakersfield, Calif. She is first editor of the only comprehensive text/reference book on vision rehabilitation following brain injury, Vision Rehabilitation: Multidisciplinary Care of the Patient Following Brain Injury, (Suter & Harvey, CRC Press, 2011). In addition to her private practice, Suter served as codirector of the California State University Bakersfield Vision Laboratory for more than 20 years and spent 17 years as the primary vision consultant to the Centre for Neuro Skills brain injury rehabilitation center in Bakersfield.
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