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A Sample Case: A boy 6 years of age was noticed by his mother as becoming increasingly listless. He complained of morning headaches. The child also began to vomit for no apparent reason. The mother at first thought that the child had some sort of stomach virus but it was his stumbling gait which made his mother seek medical advice.

The child was referred to a neurologist when the pediatrician discovered papilledema which signaled increased intracranial pressure. Examination revealed that the child had double vision and the eyes oscillated horizontally (nystagmus). There was a mild sensory loss and motor weakness on one side of the face. The child walked with a wide-based truncal ataxia. Radiologic imaging revealed 1) dilated lateral and 3rd ventricles and 2) a mass growing from the posterior part of the cerebellar vermis, filling the 4th ventricle and infiltrating its floor. Pathologic examination revealed a medulloblastoma which is considered an embryonic tumor arising from cells in the cerebellum.

Explanation -

The expanding tumor blocked the egress of cerebrospinal fluid from the ventricular system causing increased intracranial pressure, dilated ventricles, and headache. Pressure and/or infiltration by the malignant cells into the floor of the 4th ventricle impacted on nuclei of the vagus and vestibular nerves causing the vomiting and nystagmus. The broad-based gait and truncal ataxia is a sign of injury to the midline cerebellum (vermis). Interference with the nearby MLF and abducens nuclei would account for the diplopia; the asymmetrically expanding tumor has interfered with the descending tract of spinal V and the facial motor root producing the mild sensory and motor findings of the face.