Posterior fossa tumor masquerading as anterior canal BPPV.

Timothy C. Hain, MD •Page last modified: March 8, 2021


A woman in her 20's presented with positional vertigo, tinnitus and headache. The vertigo began about five to six months ago with a sensation as if she was going to pass out. There is also a pulsatile and whooshing sound. Dizziness is daily, lasting about 30 minutes. The dizziness is a spinning sensation accompanied by nausea, sometime vomiting, jumping vision, and lightheadedness.

There are also headaches with accompanying phonophobia, intolerance to strong smells, and motion intolerance. These are likely migraine. She had been diagnosed as having BPPV on the right in the past.

On examination:

Under video Frenzel's goggles, there is a low-amplitude, right-beating nystagmus. There is no nystagmus on hyperventilation. The vertebral artery test is negative. Vibration induces a low amplitude right beating nystagmus. On positional testing with head left, there is down beating nystagmus and torsional nystagmus about 3/10 overall in intensity. This is the typical pattern for right-sided anterior canal benign paroxysmal positional vertigo.


This patient has classic signs and symptoms of migraine as well as the physical findings of AC-BPPV. Nevertheless, in addition to treatment aimed at these two diagnoses, she was sent for an MRI of the brain.


Axial image of tumor of posterior fossa, compressing medulla and cerebellum.


Her MRI showed a tumor of the cerebellum, probably an ependymoma.


Unlike the situation with PC-BPPV, which is never caused by central nervous system lesions, positional vertigo having the pattern of either anterior canal or lateral-canal BPPV is rarely due to cerebellar mass lesions.

In this patient, had no MRI been done, it seems likely that she would have deteriorated neurologically and done worse. Thus there is a risk of missing the diagnosis of a more serious problem in AC-BPPV. This example leads one naturally to wonder whether or not individuals making this diagnosis such as physical therapists, but who are acting without physician oversight, may need more comprehensive malpractice insurance than those who are not.

In our practice in Chicago, we have seen several other patients with similarly located masses in the fourth ventricle, who presented with positional nystagmus.