188Chapter 11: Over-ordering tests

deficit of a migraine attack (usually visual, occasionally sensory or motor) resolves completely within 30 to 60 minutes. More prolonged persistence of a focal deficit suggests an ischemic complication or the possibility of a different underlying cause. If a patient thinks that vision has not fully returned to normal after an episode, and in cases with other atypical features, it is important to obtain visual field testing to look for a persistent defect.

The definition of migraine includes the tendency to have recurrent attacks; it is not possible to make a diagnosis of migraine based on a single episode. The clinician should be extremely careful when attributing a patient’s symptoms to a first migraine attack, especially considering that the typical symptoms, namely headache, nausea and vomiting, are the same as those of increased intracranial pressure, meningitis and subarachnoid hemorrhage. For a patient with a first episode of isolated visual loss not accompanied by headache, neuro-imaging is not indicated if the clinical features of the attack are typical.

Putting together these clinical features, the indications for neurodiagnostic investigation in a patient with suspected migraine should include: a prolonged visual field defect or other persistent focal neurologic deficit and attacks always localized to the same area. A recent change in pattern (frequency, duration or quality) without explanation (i.e. a change in trigger factors) should also prompt additional testing. The above patient illustrates a common change in pattern: women who have migraine headaches in their teens and twenties often find that their headaches resolve with pregnancy but migraine recurs during peri-menopause in the form of visual aura without headache. In patients with recurrent episodes and typical clinical features, ancillary testing is not needed.

Diagnosis: Migraine aura

Tip: The slow spread of photopsias across the visual field is the most distinctive feature indicating migraine as the cause of transient binocular visual loss.

Unexplained visual loss

Case: A 19-year-old college student experienced new onset of headaches and episodes of transient visual loss during midterm exams. Following one of her episodes the vision in her left eye failed to return. She described total blackness of vision and on examination claimed she was barely able to see light in that eye. Fundus appearance was normal bilaterally, as were all tests of vision in her right eye including normal visual field by confrontation. Pupillary responses were brisk and symmetric with no RAPD. An MRI of brain and orbits and a variety of blood tests were unrevealing. Her headaches persisted and two weeks later vision in her left eye remained bare light perception.

What feature in this case suggests nonorganic visual loss? Is additional ancillary testing needed?

This degree of visual loss (near-complete blindness in one eye) with clear ocular media is incompatible with a normal pupillary response and strongly suggests non-organic visual loss. Visual acuity was remeasured using crossed cylinders to fog the vision in the patient’s right eye. With the fellow eye so blurred that she could only be reading with the “bad” left eye, she was able to easily and accurately read the entire eye chart from the large E down to the 20/20 line. Based on this observation, a diagnosis of non-organic visual loss was made. She was reassured that her vision would return to normal and received treatment for her tension-vascular headaches.

Discussion: Non-organic (functional) visual loss is a common neuro-ophthalmic problem, encompassing malingering (feigned loss) and hysteria (also referred to as a conversion disorder). This diagnosis should be suspected when the clinical findings are inconsistent with each other or when symptoms or signs do not conform to recognized disease patterns. Visual loss may affect one or both eyes,