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The neuritis with a normal head impulse

A 41-year-old with acute vertigo and a normal lateral head impulse — but selective evidence of saccular dysfunction.

The case

A 41-year-old librarian presents with acute persistent vertigo that began 48 hours ago. The clinical picture is otherwise typical for an acute vestibular syndrome — continuous symptoms, nausea, lateropulsion to the left, no auditory features, no headache.

Examination shows spontaneous right-beating horizontal-torsional nystagmus that obeys Alexander's law and is suppressed by fixation. Head-impulse testing is unequivocally normal — no catch-up saccades on either side. There is no skew on cover testing.

A subsequent cervical VEMP shows an absent response on the left at threshold 95 dBnHL with a normal response on the right. Ocular VEMPs are symmetric and within normal limits. Pure-tone audiometry is normal bilaterally.

Caloric testing the following week shows symmetric responses bilaterally.

Question

What is the single most likely diagnosis?

Teaching point

Vestibular neuritis is a divisional disease — the superior and inferior divisions of the vestibular nerve can be selectively affected. Superior-division neuritis (90% of cases) shows abnormal head impulse and caloric paresis with normal cVEMP and posterior canal function. Inferior-division neuritis (5–15%) shows the reverse: normal head impulse and caloric responses but absent cVEMP and sometimes positional findings from the affected posterior canal. A patient with an acute vestibular syndrome but a normal head impulse should not be assumed to be central — selective inferior neuritis is the alternative explanation, and cVEMP testing distinguishes it.

References

  1. [1]Strupp M, Bisdorff A, Furman J, Hornibrook J, Jahn K, Maire R, Newman-Toker D, Magnusson M. Acute unilateral vestibulopathy/vestibular neuritis: diagnostic criteria. Consensus document of the Committee for the Classification of Vestibular Disorders of the Bárány Society. Journal of Vestibular Research 2022;32(5):389–406. doi:10.3233/VES-220201
  2. [2]Halmagyi GM, Curthoys IS. A clinical sign of canal paresis. Archives of Neurology 1988;45(7):737–739. doi:10.1001/archneur.1988.00520310043015
Related moduleVestibular Neuritis →