CEREBELLOPONTINE (CP) ANGLE TUMOUR ..... What is in a name ?!
Tumours involving the Cerebellopontine (CP) angle region are common almost representing 6 to 10 % of all intracranial tumours. Acoustic neuromas, which are also known as Vestibular schwanommas are the commonest type of tumour in this region. This is followed by another type called Meningioma, and both together account for almost 85 – 90% of the lesions on the CP angle region. Often the tumours of this region are benign, that is they belong to the non cancerous (non malignant) group. Rarely skull base sarcomas, carcinomas and metastasis can present in this region (less than 2 % are malignant).
SYMPTOMS AND SIGNS
Hearing loss is the commonest symptom which is present in 95% of the cases of CP angle tumours. This is followed by ‘Tinnitus’ (ringing or buzzing in the ears), and is the presenting complaint in more than 70% of the patients. Unsteadiness while walking, headache, facial numbness, double vision and decrease in taste sensation are the other symptoms associated with tumours in this region. Usually the symptoms are of insidious onset and progresses gradually over a period of time, as these tumours are generally slow growing in nature. The symptoms and signs arise due to direct compression of the neural structures like cranial nerves, brainstem and cerebellum. At times the tumour becomes large enough to cause obstruction to CSF (cerebrospinal fluid) pathways leading to hydrocephalus and raised intracranial tension. If this progression of symptoms are unchecked, it can lead to coma, respiratory depression and death !
DIAGNOSIS & TREATMENT
MRI with gadolinium contrast is the diagnostic procedure of choice which will show clear demarcation of the tumour from the normal brain structures whose sensitivity or tumour pick up rate is close to 98% MR-Angiogram will show displacement of the blood vessels and the vascularity of the tumour in addition (meningiomas and other skull base tumours). CT scan brain will show any widening of the bony canal or erosions if any caused by the tumour in the cerebellopontine angle region.
Microsurgical resection of the tumours is advocated in large tumours ooccupying the CP angle. The age and medical condition of the patient, the pathological behaviour of the tumour are taken into account before planning on the type of surgery offered. Due to significant number of vital neurological structures are closely associated with these tumours, excision of the lesions are undertaken with utmost care with the aid of high magnification microscope, ultrasonic surgical aspirator (CUSA or SONOCA) and of course facial nerve and brainstem neurophysiological intraoperative monitoring. Small tumours and residual lesions can be tackled by radiation therapy (X knife, Gamma knife or Cyber knife radiosurgery will be ideal for this location). If hydrocephalus present, a ventriculo peritoneal shunt or a endoscopic ventriculostomy is required in addition to the tumour surgery.
Dr. M. J. Arunkumar, M. Ch., DNB Senior Consultant Neurosurgeon Hannah Joseph Hospital Madurai