This tumor originates in arachnoidal cells along the cribriform plate. The diagnosis depends on the finding of ipsilateral or bilateral anosmia or ipsilateral or bilateral blindness—often with optic atrophy and mental changes. The tumors may reach enormous size before coming to the attention of the physician but as many are small and found incidentally with cerebral imaging (see Fig. 30-7B). If the anosmia is unilateral, it is rarely if ever reported by the patient. The unilateral visual disturbance may consist of a slowly developing central scotoma. Abulia, confusion, forgetfulness, and inappropriate jocularity (witzelsucht) are the usual psychic disturbances from compression of the inferior frontal lobes (see Chap. 21). The patient may be indifferent to or joke about his blindness. Usually there are radiographic changes along the cribriform plate. MRI with gadolinium is diagnostic. Except for the largest and most invasive tumors, surgical removal is possible.
Meningioma of the Tuberculum Sella
Cushing was the first to delineate the syndrome caused by this tumor. All of his 23 patients were female. The presenting symptoms were visual failure—a slowly advancing bitemporal hemianopia with a sella of normal size. Often the field defects are asymmetrical, indicating a combined chiasmal–optic nerve involvement. Usually there are no hypothalamic or pituitary deficits. If the tumor is not too large, complete excision is possible. If removal is incomplete or the tumor recurs or undergoes malignant changes, radiation therapy of one type or another is indicated. The outlook is then guarded; several of our patients succumbed within a few years.
Glioma of the Brainstem
Astrocytomas of the brainstem are relatively slow-growing tumors that infiltrate tracts and nuclei. They produce a variable clinical picture depending on their location in the medulla, pons, or midbrain. Most often, this tumor begins in childhood (peak age of onset is 7 years), and 80 percent appear before the 21st year. Symptoms have usually been present for 3 to 5 months before coming to medical notice. In most patients the initial manifestation is a palsy of one or more cranial nerves, usually the sixth and seventh on one side, followed by long tract signs—hemiparesis, unilateral ataxia, ataxia of gait, paraparesis, and hemisensory and gaze disorders in addition to pseudobulbar dysarthria and palsy. In the remaining patients the symptoms occur in the reverse order—that is, long tract signs precede the cranial nerve abnormalities. Patients in the latter group survive longer than those whose illness begins with cranial nerve palsies. Headache, vomiting, and papilledema may occur, usually late in the illness. The course is slowly progressive over several years unless some part of the tumor becomes more malignant (anaplastic astrocytoma or glioblastoma multiforme) or, as rarely happens, spreads to the meninges (meningeal gliomatosis), in which instance the illness may terminate fatally within months.
The main problem in diagnosis is to differentiate this disease from a pontine form of multiple sclerosis, a vascular malformation of the pons (usually a cavernous hemangioma), or brainstem encephalitis, and to distinguish the focal from the diffuse type of glioma (see in the following text). The most helpful procedure in diagnosis and prognosis is contrast-enhanced MRI (Fig. 30-22).