From the Guidelines
For a patient with low B12 levels presenting with vestibular and migraine symptoms, I recommend checking complete blood count (CBC) with peripheral smear, homocysteine, methylmalonic acid (MMA), folate, ferritin, iron studies, thyroid function tests (TSH, free T4), vitamin D level, inflammatory markers (ESR, CRP), and electrolytes including magnesium. These tests help establish the severity and cause of B12 deficiency while exploring other potential contributors to neurological symptoms.
- CBC can reveal macrocytic anemia often associated with B12 deficiency, while elevated homocysteine and MMA provide more sensitive indicators of functional B12 deficiency 1.
- Folate should be checked as deficiencies often coexist and can cause similar neurological manifestations.
- Thyroid dysfunction can mimic or exacerbate vestibular symptoms, and magnesium deficiency is linked to migraine and vestibular disorders.
- Vitamin D deficiency may contribute to neurological symptoms, and inflammatory markers help rule out inflammatory causes of vestibular dysfunction.
- Iron studies are important as iron deficiency can cause similar neurological manifestations and often coexists with B12 deficiency. Given the potential for central causes of vertigo, such as posterior circulation infarct, and the importance of early diagnosis and treatment, careful consideration of the patient's overall clinical presentation and the use of bedside tests like the HINTS examination is crucial 1. The most recent guidelines on vitamin B12 deficiency emphasize the importance of prompt treatment and the consideration of neurological involvement in determining the approach to replacement therapy 1. Overall, a comprehensive approach to diagnosing and managing B12 deficiency, considering both the hematological and neurological aspects, is essential for improving patient outcomes.
From the FDA Drug Label
Laboratory Tests During the initial treatment of patients with pernicious anemia, serum potassium must be observed closely the first 48 hours and potassium replaced if necessary Hematocrit, reticulocyte count, vitamin B12, folate and iron levels should be obtained prior to treatment. If folate levels are low, folic acid should also be administered Repeat determinations of iron and folic acid may reveal a complicating illness that might inhibit the response of the marrow Persons taking most antibiotics, methotrexate and pyrimethamine invalidate folic acid and vitamin B12 diagnostic blood assays
The patient with low B12 and vestibular and migraine symptoms should have the following labs checked:
- Hematocrit
- Reticulocyte count
- Folate levels
- Iron levels
- Serum potassium 2
From the Research
Laboratory Tests for Vestibular and Migraine Symptoms with Low B12
To further investigate the patient's condition, the following laboratory tests may be considered:
- Complete blood count (CBC) to assess for any underlying anemia or other blood-related disorders 3
- Serum methylmalonic acid measurement to confirm vitamin B12 deficiency in asymptomatic high-risk patients with low-normal levels of vitamin B12 3
- Audiometric examination to evaluate for any auditory dysfunction, as vitamin B12 deficiency has been associated with cochlear damage and auditory dysfunction 4
- Vestibular-evoked myogenic potential (VEMP) testing to assess for any vestibular hypofunction, as patients with vitamin B12 deficiency have been shown to have increased rates of absent VEMPs and decreased amplitudes 4
- Serum homocysteine level to assess for hyperhomocysteinemia, which has been associated with impaired microarterial flow, demyelization, and neuronal damage 4
Considerations for Vestibular Migraine
In patients with suspected vestibular migraine, the following considerations may be taken into account:
- Screening for other comorbidities, such as mood disorders, particularly anxiety, which are often found in patients with vestibular migraine 5, 6
- Assessment for other migrainous features, such as photophobia, phonophobia, osmophobia, and visual aura, which can accompany vestibular migraine attacks 5
- Evaluation for other vestibular symptoms, such as spontaneous vertigo, triggered vertigo, positional vertigo, and head-motion dizziness, which can manifest in patients with vestibular migraine 5