Benign Intracranial Hypertension is a clinical entity usually afflicting obese women who suffer from a venous hum, headache and blurry vision. Importantly the venous hum, even unilaterally, can be the only presenting symptom.

Clinically it can be diagnosed by compressing the ipsilateral jugular vein causing the venous hum to disappear. Except for the rarely diagnosed condition of sinus thrombosis. Magnetic resonance angiography and magnetic resonance imaging are usually negative and the diagnosis is confirmed by lumbar puncture (pressure > 20 cm water).

Treatment consists of weight loss, diuretics or ventriculoperitoneal or lumboperitoneal shunting.

Pre-operative

Postoperative with shunt

Carotid Stenosis is the most frequent cause of arterial pulsatile tinnitus. The pulsatile tinnitus disappears on compressing the ipsilateral, internal carotid artery. Diagnosis can be confirmed by angiography. Treatment of the extracranial carotid artery stenosis consists of dilation and stenting or carotid endartrectomy.

As for the rarer intracranial carotid artery stenosis two approaches can be followed. An initial balloon occlusion test under transcranial doppler and E.E.G. monitoring can verify whether the ipsilateral carotid artery can be sacrificed. If so, one option is to ligate the symptomatic carotid artery. The other option is to dilate and stent the intracranial portion of carotid artery resulting in a disappearance of the arterial pulsatile tinnitus.

A major problem still faced today is that stents tend to occlude, and thus this elegant technique still remains experimental until the coagulation problems are better controlled.

Glomus Tumours, or paraganglioma, are found in women presenting with unilateral hearing loss and pulsatile tinnitus. As they are benign lesions growing to less than 2 cm in five years, treatment options are a "wait and see" policy or embolisation and surgery.

Other Vascular Lesions of the Petrous Bone or Skull Base such as hemangiopericytoma, plasmacytoma, giant cell tumours amongst others are also known to generate a treatable pulsatile tinnitus.

Dural Arteriovenous Malformations (A.V.M.) result from chronic mastoiditis or other causes leading to occlusion of the sigmoid-transverse sinus.

Vascular bypasses develop around the occlusion resulting into a dural A.V.M. If the dural A.V.M. is symptomatic or if it is asymptomatic with leptomeningeal drainage these lesions should be embolized, usually in multiple sessions.

If intractable with endovascular treatment surgical excision of the A.V.M. and dura can be proposed.

A Brain Tumour compressing the auditory cortex can cause a non-pulsatile tinnitus as the sole symptom, probably due to a direct influence on normal cortical sound processing. Removal of the lesion results in abolishing the tinnitus. Tumours elsewhere along the auditory tract, for example the brainstem, usually give rise to additional symptoms, related to the closeness of other neural structures.

Microvascular Compressions of the cochlear nerve can cause incapacitating high pitch non-pulsatile tinnitus, unless the vascular loop enters the internal auditory canal, in which case the osseous conduction gives rise to an arterial pulsatile tinnitus. This difficult diagnosis is based on the clinical picture and confirmed by auditory brainstem evoked potentials and magnetic resonance imaging.

Results of microsurgical vascular decompression are related to the surgical delay, the preoperative hearing status, MRI imaging and gender. In general we can state that if the tinnitus has been present for less than three years, if there is a useable or normal hearing, and the MRI demonstrates a vascular compression - in women - the results can be good. Vascular compressions of the vestibulocochlear nerve are found in many asymptomatic patients (12.5% and 21.5% respectively) but this discrepancy is also noticed in trigeminal neuralgia (14%) and even in herniated lumbar discs (36%), where this is not considered an argument to doubt about the pathophysiological importance of the neural compression.

After surgery, the tinnitus can be expected to disappear completely if there is a significant amelioration within the first 72 hours. If this rapid amelioration does not occur, it can take several weeks or even months before the tinnitus improves, but complete resolution is usually not expected.

In Ménière's Disease any kind of surgery, whether vestibular nerve section, cochlear nerve section, endolymphatic sac surgery or gentamicin injections, never seems to produce greater than 50% tinnitus control - a marginal improvement upon the 30% spontaneous disappearance in its natural history.

In Otosclerosis relief of the non-pulsatile tinnitus by successful stapedectomy can be expected in about 40 to 64%.

In Vestibular Schwannoma (AKA Acoustic Neuroma) the high pitch tinnitus (ringing or steam from a kettle) is present in 60 to 85% of the patients. Currently, vestibular schwannomas are often treated by radiosurgery. This seems to have almost no effect on the tinnitus whereas in microscopic surgery 40 to 50% of the tinnitus disappears. Unfortunately microsurgery also creates tinnitus in many patients.

     The Chiari Malformation is a clinical entity in which there is a tonsillar herniation into the foramen magnum. 7 to 10% of these patients suffer from tinnitus and it can be both non-pulsatile and pulsatile.

The pulsatile tinnitus consists of a venous hum caused by raised intracranial pressure and worsens on bending over, but disappears on ipsilateral jugular vein compression, which also results in an improvement of the hearing (masking). No brainstem auditory evoked potential changes are noted in this kind of tinnitus. After the surgical decompression this form of tinnitus disappears.

     The non-pulsatile tinnitus on the other hand is usually intermittent and the cause is not known. It is either due to stretching of the cochlear nerve, e.g. by microvascular compression, or to brainstem traction. Brainstem auditory evoked potential changes are noted in 75% of the patients and consist of an IPL III-V prolongation in 100% of the patients (brainstem traction and/or contralateral microvascular compression ?) and in 30% of IPL I-III prolongation (ipsilateral microvascular compression ?).

Posterior fossa decompression which consists of opening the foramen magnum and widening the dura mater results in abolishing the non-pulsatile tinnitus if tinnitus is of recent origin.

Arachnoid cyst is a rare cause of non-pulsatile tinnitus. It is a congenital or posttraumatic/post inflammatory disorder leading to vague symptoms. Arachnoid cysts producing tinnitus can occur in the CP angle, but also retroclival and retrocerebellar. Usually symptoms of intracranial hypertension are associated with non-pulsatile tinnitus. Surgical treatment consists of marsupialization or excision of the cyst.

Other Cerebellopontine Angle Lesions (CPA) such as meningiomas, epidermoid tumours, lipomas, choroid plexus papillomas, epithelial cysts, teratomas, cavernomas, and hemangiomas can present with non-pulsatile tinnitus, usually with associated symptoms depending on the location of the lesion and the degree of brainstem, cerebellar or cranial nerve compression.

Electrical stimulation of the auditory cortex is a new kind of treatment based on the working mechanism of how tinnitus arises. An electrically active electrode is placed on the area of cortical reorganization, ie. the zone where braincells are looking for a new job. By means of stimulating those braincells electrically they are prevented from growing into the neighbouring areas. In other words the normal internal neural stimulation of those braincells is taken over by external electrical stimulation.

In a clinical setting two problems must be solved. First of all the exact localisation on the brain of the auditory cortical reorganization has to been demonstrated. This is done by means of a functional MRI. This is a classical MRI scan where two scans are combined : a normal brainscan and a scan performed during auditory exposure.

The second problem is retrieving the zone of cortical reorganization as demonstrated on the scanner exactly on the patient' s brain. Therefore neuronavigation is used guided by the funtional MRI. The navigation system is basically a GPS system specifically adapted for brain surgery. Thus the functional MRI, demonstrating the area of the organization is put on a CD-Rom which is then inserted in the neuronavigation system similar to the map of a country or city that is being downloaded into a GPS system.

When this is ready, a non invasive way of demonstrating the efficacy of the stimulation is performed by means of transcranial magnetic stimulation guided by the navigation system. If this non invasive test is succesful in suppressing the tinnitus, at a later stage an electrode can be placed extradurally on the auditory cortical zone of reorganisation (on the exact same site as where the transcranial magnetic stimulation was successful). The electrode is activated and powered by a battery that is implanted in the abdomen. Via a remote control the stimulation parameters (frequency, amplitude and pulse width) can be changed postoperatively to find the best parameters for maximal tinnitus control.