Examine this patient's cranial nerves.
Damage to the seventh and eighth cranial nerves is the hallmark of this lesion in this region.Proceed as follows:· Check the corneal reflex and test the trigeminal nerve· Tell the examiner that you would like to look for the following:-Cerebellar signs -Signs of neurofibroma type 2
-Papilloedema (seen uncommonly as a result of raised intracranial pressure).
This patient has features of cerebellopontine angle tumour (lesion) usually due to an acoustic neuroma (aetiology), and has severehearing loss (functional status).
Mention a few causes of cerebellopontine angle lesions.
· Acoustic neuroma.· Meningioma, cholesteatoma, haemangioblastoma, aneurysm of the basilar artery.· Pontine glioma.· Medulloblastoma and astrocytoma of the cerebellum.· Carcinoma of the nasopharynx.· Local meningeal involvement by syphilis and tuberculosis.
What do you understand by the term 'cerebellopontine angle'?
It is the shallow triangular fossa lying between the cerebellum, lateral pons and the inner third of the petrous temporal bone. Itextends from the trigeminal nerve (above) to the glossopharyngeal nerve (below). The abducens nerve runs along the medial edge,whereas the facial and auditory cranial nerves transverse the angle to enter the internal auditory meatus.
What is the histology of acoustic neurofibroma?
It consists of elongated cells similar to spindle fibroblasts with much collagen and reticulum. They are believed to arise fromSchwann cells and are also known as schwannomas.
How would you investigate such patients?
· Skull radiography, tomography of the internal auditory meatus, and CT head scan.· Serology for syphilis.· Audiography.· Caloric test (which will reveal that the labyrinth is destroyed).· Vertebral angiography.· CSF: may be abnormal or have raised protein concentration.· MRI.
What is the treatment in this condition?
· Microsurgical resection.· Stereotactic radiosurgery (N Eng1,1 Med 1998; 339: 1426-33).· Conservative approach.F.T. 5chwann (1810-1882), a German anatomist, was Professor of Anatomy in the Louvain. He was one of the first to demonstratethat fermentation was associated with living organisms. Independently from Schleiden, he concluded that plants are formed of cells;this is known as the Schleiden-Schwann cellular theory. Schwann also discovered that the upper oesophagus contains striatedmuscle. He discovered pepsin and showed that bile was essential for digestion.The first surgical removal of an acoustic neuroma was performed in 1894 (N Engl J Med 1998; 339: 1471).L. Leksell was the first to use radiosurgery - what he called the 'gamma knife' (Acta Chir Scand 1971; 137: 763-5).