A 29-year-old woman presented with blurred vision of 2 week’s
duration. She had consulted an optometrist to have her eyeglass
prescription checked and was told that she should visit a doctor.
She had a six-month history of intermittent headaches and diminished
hearing on the right. She had been to a doctor on two prior occasions
for the headache and was prescribed a mild analgesic with some relief.
She had mentioned the hearing loss to the doctor, but no further
work up was done.
On examination, she was a healthy
appearing woman in no distress. There was markedly diminished hearing
on the right. The Weber test localized to the left. Pupillary response
and extraocular motion were intact, with slight rotary nystagmus
in all directions. There was diminished sensation on the right side
of the face. The right corneal reflex was diminished. The gag reflex
was also diminished on the right. The tongue was midline. Visual
acuity with corrective lenses was 20/25 right eye, 20/30 left
eye. Funduscopic examination revealed bilateral papilledema and
- What is this patient’s diagnosis?
Her head CT is shown in Figure 1.
The clinical presentation of this patient is classic for an acoustic schwannoma (formerly called
acoustic neuroma) or other cerebello-pontine angle tumor. Unfortunately,
diagnosis of this disease is occasionally delayed because of its
gradual onset and a failure to appreciate the significance of unilateral
hearing loss. In this patient, the tumor had grown to a large size causing
obstructive hydrocephalus and papilledema.
Tumors (and abscesses) can often be detected on noncontrast CT because the lesions
are hypo- or hyperattenuating (appear darker or lighter) relative
to normal brain tissue. In addition, surrounding edema and mass
effect distorts other anatomical structures. Lesions in the posterior
fossa are, however, often difficult to detect by CT. This is because
adjacent thick cortical bone creates beam-hardening artifacts, which
diminish the ability of CT to visualize anatomical detail and to
detect slight differences in tissue density (Figure 1, images 10 and
In this patient, the right side
of the cerebellum has slightly lower attenuation (appears darker)
than the left (Figure 1, images 8 and 9). More importantly, the
fourth ventricle is compressed and displaced toward the left, which
indicates that the tumor is on the right and compressing the cerebellum
and brainstem. In ...