Rehabilitation of hearing and communication functions in patients with NF2.

Most patients with neurofibromatosis type 2 (NF2) lose hearing either spontaneously or after removal of their neurofibromas. The patient may benefit from conventional hearing aids if, due to modern microsurgery and intraoperative monitoring the integrity of the cochlea and the 8th nerve is preserved. With lost auditory function but preserved electrical stimulibility of the 8th nerve a cochlear implant may be appropriate. But if the patients have no remaining 8th nerve to stimulate, there is no benefit from cochlear implants. Until some years ago, vibrotactile aids, lip-reading, and sign language have been the only communication modes available to these patients. With auditory brain stem implants it is now possible to bypass both the cochlea and the 8th nerve and to stimulate the cochlear nucleus directly. Stimulation of the devices produces useful auditory sensations in almost all patients. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores and the ability to converse on the telephone. Also lip-reading is significantly improved with brain stem implants. The successful work of an auditory brainstem program center depends very much on the close interdisciplinary collaboration between the Departments of Neurosurgery and ENT-surgery. In the future new developments like speech processing strategies and new designed electrodes accessing the complex tonotopic organization of the cochlear nucleus may further improve rehabilitation in these patients who would have been deaf some years ago.

Functional magnetic resonance imaging of human pontine auditory pathway.

The purpose of this study is to visualize brainstem auditory pathways by functional magnetic resonance imaging (fMRI). Eighteen healthy volunteers (age 28 to 42 years) with normal hearing function underwent fMRI examination on a 1.5 Tesla imaging system (Philips, Best, The Netherlands) with periodic click stimulation. Blood oxygen level dependent images were obtained using a three-dimensional EPI sequence with shifted echo technique (principles of echo shifting with a train of observations). Control scans without click stimulation were obtained in the identical setting. Cross correlation activation maps were calculated using a postprocessing tool (Philips). They were matched with anatomic slices of identical orientation and thickness. Five of 18 subjects were excluded because of motion artifacts. In 4/13 significant activation was observed at the root entry zone of the ipsilateral acoustic nerve corresponding to the cochlear nuclei. In 11/13 subjects, significant activation was found in the same slice contralaterally close to the floor of the 4th ventricle, corresponding to the expected region of the superior olivary nucleus. Activation of the rostral parts of the auditory pathway (inferior colliculus, medial geniculate body) was not found. In the absence of the stimulus no activation occurred in these structures. It was concluded that activation of the brainstem auditory pathways by click stimuli can be visualized by fMRI.

Augmentative treatment of chronic deafferentation pain syndromes after peripheral nerve lesions.

Deafferentation pain syndromes developing after peripheral nerve lesions are difficult to treat. According to the follow-up (mean: 39.5 months) of 6 patients suffering from causalgic pain we will present our method of augmentative therapy in chronic neuropathic pain caused by peripheral nerve lesions, i.e., peripheral nerve stimulation (PNS), spinal cord stimulation (SCS) and chronic intrathecal opioid infusion. None of the patients showed intraoperative or follow-up complications. Evaluated by visual analogue scales all patients reported a good to excellent pain relief (75-100%). (1) Regarding the favourable long-term results of PNS, this method should be considered in cases of mononeuropathic pain syndromes. (2) Neuropathic pain syndromes which are not assignable to a singular nerve lesion, can often be managed effectively by SCS. (3) In contrast to the widespread opinion, deafferentation pain syndromes of central or peripheral origin can be treated satisfactorily by intrathecal opiate administration.

Surgery of intrinsic cerebral neoplasms in eloquent areas under local anesthesia.

28 patients with a mean age of 43.6 years were operated on for a cerebral neoplasm situated in close proximity to an eloquent area (24 speech area, 4 motor cortex) from 1996 to 1999. Preoperatively, all patients had undergone a detailed neuropsychological examination. In 10 patients aphasic disturbances could be detected. All patients underwent preoperative PET studies (methionine and (15)O-labeled water with activation during speech or finger tapping). These were performed and co-registered with MRI data to demonstrate the topographical relationship between motor or language function and the tumor borders. Anesthesia was induced with i.v. administration of propofol (150-250 mg/h). Craniotomy was performed under local infiltration anesthesia. After opening of the dura, sedation was stopped and operation was continued with the patient being alert and co-operative. With close clinical observation during electrical cortex stimulation, a speech arrest could be triggered or avoided. The motor cortex was identified by recording the phase reversal of the contralateral SEP of the median nerve and by direct cortical stimulation. As soon as aphasic or motor disturbances appeared, the tumor removal was continued with the goal of avoiding these specific regions. In 27 patients, preexisting neuropsychological and neurological deficits did not worsen. Only one patient was left postoperatively with a major permanent aphasic deficit that was present preoperatively to a minor degree. The use of local anesthesia in craniotomy for surgery of intrinsic cerebral neoplasms in eloquent areas allows for a continuous and repetitive monitoring of speech and motor function during the removal of even those tumors that were previously considered inoperable.

Somatostatin receptor imaging in intracranial tumours.

The somatostatin analogue [111In-DTPA-d-Phe1]-octreotide (111In-octreotide) allows scintigraphic visualization of somatostatin receptor-expressing tissue. While it is well known that a large variety of tissues express somatostatin receptors and 111In-octreotide scintigraphy has a clearly defined role in various neuroendocrine diseases, the clinical value of 111In-octreotide scintigraphy in brain tumours is still under clinical investigation. In 124 patients with 141 brain lesions (63 meningiomas, 24 pituitary adenomas, 10 gliomas WHO class I and II, 12 gliomas WHO class III and IV, 11 neurinomas and 2 neurofibromas, 7 metastases and 12 other varieties: three non-Hodgkin B-cell lymphomas, two epidermoids, one abscess, one angioleiomyoma, one chordoma, one haemangiopericytoma, one osteosarcoma, one plasmacytoma and one pseudocyst), 111In-octreotide scintigraphy was performed 4-6 and 24 h after i.v. injection of 110-220 MBq 111In-octreotide. Planar images of the head in four views with a 128x128 matrix and single-photon emission tomographic images (64x64 matrix) were acquired, and lesions were graded according to qualitative tracer uptake. Fifty-nine of the 63 meningiomas showed moderate to intense tracer uptake. Nine of 24 pituitary adenomas were visible; the remaining 15 did not show any tracer uptake. None of the class I and II gliomas with an intact blood-brain barrier were detected whereas 11/12 class III and IV gliomas showed 111In-octreotide uptake. None of the neurinomas or neurofibromas were positive. Five of seven metastases were classified as positive, as were the osteosarcoma, two of three non-Hodgkin B-cell lymphomas, one abscess, one angioleiomyoma, one chordoma and one haemangiopericytoma. The other varieties (one non-Hodgkin B-cell lymphoma, two epidermoids, one plasmacytoma and one pseudocyst) did not show 111In-octreotide uptake. The results demonstrate that a large variety of intracranial lesions express somatostatin receptors and therefore can be visualized by [111In-DTPA-d-Phe1]-octreotide scintigraphy. This technique can be valuable in the differentiation between meningiomas and pituitary adenomas, based on qualitative tracer uptake. [111In-DTPA-d-Phe1]-octreotide scintigraphy allows differentiation between meningiomas and neurinomas or neurofibromas and therefore provides complementary information to computed tomography or magnetic resonance imaging. Furthermore, this technique allows differentiation between scar tissue and recurrent meningiomas postoperatively and can help in non-invasive tumour differentiation of multiple intracranial lesions, which can be of value in defining the most adequate therapeutic strategy.