Evidence of peripheral auditory activity modulation by the auditory cortex in humans.

At the auditory periphery, the medial olivocochlear system is assumed to be involved in complex sound processing and may be influenced by feedback from higher auditory nuclei. Indeed, the descending auditory pathway includes fibers coming from the auditory cortex that are anatomically well positioned to influence the superior olivary complex, and thus the medial efferent system. The aim of the present study was to verify the hypothesis of an implied influence of the auditory cortex on the peripheral auditory system. In three rare cases of patients presenting with intractable temporal lobe epilepsy, Heschl's gyrus (i.e. the temporal superior gyrus) was surgically removed in the right hemisphere in two patients and in the left hemisphere in a third patient, in order to minimize epilepsy attacks, as preoperative stereoencephalography had shown the epileptic focus or tumor to be situated in those locations. In all three cases, several weeks after the operation the medial olivocochlear system was clearly less functional on both sides, but especially on the side contralateral to the resection. In healthy controls, no such pattern was obtained. In four other epileptic patients, who were operated unilaterally at the anterior temporal pole, amygdala and hippocampus with the temporal gyrus partially spared, efferent suppression grew stronger in the ear ipsilateral to surgery. These results revealed that, in humans, the primary and secondary auditory cortex play a role in modulating auditory periphery activity through direct or indirect efferent fibers. In accordance with previous findings, this descending influence may improve the auditory afferent message by adapting the hearing function according to cortical analysis of the ascending input.

[Epidermoid cyst of the lateral ventricles]. / Kyste épidermoïde des ventricules latéraux.

A case of epidermoid cyst of the lateral ventricles is reported. The patient presented with a weakness of the left lower limb and neuropsychological disorders. The diagnosis was assessed by CT scan and MRI, and confirmed at the operation. The lesion has been largely removed through a transcallosal approach though incompletely. However the long term follow-up was uneventful. Twenty-nine cases of the literature have been reviewed.

Ventral transdural herniation of the thoracic spinal cord: surgical treatment in four cases and review of literature.

BACKGROUND: A specific cause of progressive Brown-Sequard syndrome has been identified: a ventral herniation of the thoracic spinal cord through the dural sleeve on one side. METHOD: Four female patients who were affected by a progressive Brown Sequard syndrome related to a transdural spinal cord herniation have been investigated and were submitted to surgery and postoperative evaluation. FINDINGS: The MRI scan showed atrophy and forward displacement of the spinal cord on one side and adhesion of the spinal cord to the dura mater. CT myelography demonstrated the disappearance of the premedullar rim at the level of the herniation and the shadow of the extradural herniation. Surgical treatment consisted in the excision of the arachnoid cyst when there was one, section of the dentate ligament, release of the adhesions, detachment of the spinal cord from the hernial orifice, and lastly suture of the dural tear or placement by a patch. Follow-up examination showed motor improvement with persistent sensory deficit in two cases and stabilisation in two cases. INTERPRETATION: The cause of the dural tear, either traumatic or congenital could not be confirmed in the four cases. Symptoms probably occur when herniation fills the orifice and strangulation happens which explains the late appearance and progressive evolution of this myelopathy. Mobilisation of the herniated spinal cord back into the intradural space can be achieved by surgery and may stop the evolution of the symptoms and signs.

[Intramedullary subependymoma of the cervical spinal cord. Review of the literature a propos of a case]. / Sub-épendymome médullaire cervical. Revue de la littérature à propos d'une observation.

A case of intramedullary subependymoma (SE) of the cervical spinal cord is reported. A 35 year-old female patient developed paresthesiae in her right upper and lower limbs for approximately two years. Magnetic resonance imaging (MRI) of the cervical spinal cord disclosed an intrisic medullary tumor at the C2-C3 levels, predominantly involving the right hemicord. At surgery, a subpial ependymoma was totally removed using the ultrasonic surgical aspirator with no resulting anomalies of the intraoperative somatosensory evoked responses. The patient made a good recovery. At one-year follow-up, she had resumed her previous occupation and complained only from minor sequelae. Twenty-nine spinal cord SE of the literature are detailed. It is likely that they account for less than two per cent of all spinal cord tumors. A majority of cases involved the cervical cord or the cervicothoracic junction. Signs and symptoms are similar to those of other spinal intramedullary tumors. In 17 cases explored by MRI, no specific pattern could distinguish SE from astrocytomas or ependymomas, except perhaps for a more marked tendency for SE to grow excentrically within the cord or to show an exophytic component. Spinal cord SE show pathological features grossly comparable to those described in intracranial SE with clusters of small glial cells scattered among densely packed fibers. Histogenesis of SE has been a matter of debate over years, whereas it is currently admitted that they may represent a variant of ependymomas. In conclusion, most clinical and imaging features of spinal cord SE are similar to those of other pathological varieties. Radical removal is the most appropriate treatment modality, despite inherent risk of postoperative deterioration and significant sequelae on long term follow-up.