Hoover Sign in Migraine: A Neurological Examination Finding for Functional Weakness
The Hoover sign is a clinical test used to distinguish functional (non-organic) weakness from organic neurological weakness, and it has no direct relevance to migraine-related cognitive symptoms like brain fog or word-finding difficulty. 1, 2
What is the Hoover Sign?
The Hoover sign is performed by placing your hand under the heel of the allegedly weak leg while asking the patient to flex the hip of their normal leg against resistance:
- In organic weakness: No pressure is felt under the weak leg's heel
- In functional weakness: Heightened pressure is felt under the weak leg's heel due to synergistic contraction 1
The test has moderate sensitivity (63%) but high specificity (100%) for functional weakness 1, 2. This means a positive test strongly suggests functional weakness, but a negative test doesn't rule it out.
Why This Doesn't Apply to Migraine Cognitive Symptoms
Your migraine patient with brain fog and word-finding difficulty is experiencing documented cognitive dysfunction that occurs during migraine attacks, not functional weakness:
- Objective cognitive impairment during migraine attacks includes slowed processing speed, impaired verbal memory, word-finding difficulties, and attention deficits 3, 4
- These symptoms represent reversible brain dysfunction related to altered subcortical activity affecting the hypothalamus, hippocampus, and thalamus, plus changes in brain network connectivity 5
- This is not a functional neurological disorder requiring Hoover sign testing
Important Clinical Pitfall
Do not conflate migraine-related cognitive symptoms with functional neurological disorder. While recent literature suggests Hoover's sign may relate to altered sensory processing and agency beyond just functional weakness 6, applying this test to migraine cognitive symptoms would be inappropriate and potentially harmful to the therapeutic relationship. The cognitive symptoms your patient describes are:
- Well-documented ictal (during attack) phenomena 3, 4
- Supported by objective neuropsychological testing 4
- Part of the recognized migraine symptom complex 5
The appropriate evaluation focuses on confirming migraine diagnosis using ICHD-3 criteria and assessing for red flags (thunderclap headache, atypical aura, focal neurological deficits, impaired memory beyond typical migraine-related changes) that would warrant neuroimaging 7. The Hoover sign would only be relevant if you suspected concurrent functional limb weakness, which is an entirely separate clinical question.