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Natural History of Vestibular Schwannomas
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
Mirko Tos, Sven-Eric Stangerup, Per Caye-Thomasen
Bone resorption is an active, slowly progressive process, caused presumably by increased vascularization, fibrosis and adhesions in the tumour area, where the pressure from the tumour, due to its growth, plays an important role. The degree of bone resorption of the internal acoustic meatus varies in VS. Some large and giant tumours have minor or modest bone resorption, some small- and medium-sized tumours have extensive resorption extending inferiorly as far as the cochlear aqueduct and superiorly to the middle fossa dura. Extra-meatal expansion of the tumour into the relatively large and empty pontine cistern initially develops silently (Figure 101.3). Growth and extension in this direction causes some displacement and stretching of the VIIth and VIIIth cranial nerves on the anterior aspect of the tumour and of the anterior inferior cerebellar artery (AICA) on the inferior aspect. Angioneogenesis is visible at surgery, with new small vessels running from the porus to the extrameatal portion of the tumour. After further growth, the tumour expands sufficiently to touch and compress the cerebellum and trigeminal nerve. During this process, the VIIth and VIIIth nerves are thinned or ribboned, become compressed and even more stretched. At the same time, the internal acoustic meatus continues to become more and more widened. Further growth and expansion causes compression and displacement of the brainstem and the fourth ventricle, which leads gradually to hydrocephalus.
Cheryl
Published in Walter J. Hendelman, Peter Humphreys, Christopher R. Skinner, The Integrated Nervous System, 2017
Walter J. Hendelman, Peter Humphreys, Christopher R. Skinner
There is a circulation of CSF within the ventricles, with the flow being from lateral ventricles to the third ventricle, and then via a narrow aqueduct in the midbrain to the fourth ventricle in the pontine region (black arrows in Figure 9.5). At the lower end of this ventricle, CSF ‘escapes’ into the subarachnoid space, the cerebello-pontine cistern, known generally as the cisterna magna. Cisterns are enlargements of the subarachnoid space, and several others are found around the brainstem; the largest of these is the cisterna magna, located behind the brainstem and below the cerebellum, in the posterior cranial fossa, just above the foramen magnum (see Figure 9.5).
Neurology and Non-Traumatic Spinal Imaging
Published in Gareth Lewis, Hiten Patel, Sachin Modi, Shahid Hussain, On Call Radiology, 2015
Gareth Lewis, Hiten Patel, Sachin Modi, Shahid Hussain
Careful image windowing is essential to identify subtle haemorrhage. Review areas should include the pre-pontine cistern cistern, sylvian fissures, sulcal spaces near the vertex and dependent parts of the ventricular system.
A Case Report of Bilateral Abducens Palsy in the Setting of Clival Fracture – Recovery Related to Pathophysiological Basis of Injury
Published in Neuro-Ophthalmology, 2021
Stefan Dimou, Lobna Alukaidey, Girish Nair
The course of the abducens nerve from the brainstem to the lateral rectus is long and tortuous, leaving it vulnerable to injury. Emerging from the lower border of the pons, above the medullary pyramid, it travels ventrally through the pontine cistern before turning superiorly to pierce the dura mater along the clivus and courses upwards between the layers of the dura. It then passes through the osteofibrous conduit known as Dorello’s canal at the petrous apex to pass into the cavernous sinus, where it runs adjacent to the cavernous segment of the internal carotid artery before entering the superior orbital fissure (Figure 4). Here it runs through the cone of muscles to enter the ocular surface of the lateral rectus muscle, approximately one-third of the way along.2
Efficacy of and risk factors for percutaneous balloon compression for trigeminal neuralgia in elderly patients
Published in British Journal of Neurosurgery, 2021
Ming-Wu Li, Xiao-Feng Jiang, Chao-Shi Niu
In this study, CT and 3D-Slicer software were used for all patients before surgery to reconstruct and evaluate the size of the foramen ovale. One patient’s foramen ovale was flat and surrounded by spinous bone-like protrusions. Although the puncture angle was adjusted during surgery to place the balloon catheter in the planned position, the inflated balloon appeared round, i.e., different from the pear-shaped balloon in other patients undergoing successful puncture. A pear-shaped balloon appears when the balloon extends into the pontine cistern after filling the Meckel cave. Numerous clinical studies have classified the shape of the balloon into pear-shaped, pear-like shaped, oval, round, irregular and inverted pear-shaped. A pear-like shaped balloon can provide the same pain relief effect as a pear-shaped balloon. Round shape indicates that the balloon has not entered or did not completely enter the Meckel cave and is, instead, inflated in the epidural cavity. A balloon with this shape may not produce effective treatment or may be associated with early recurrence.2
Spontaneous haemorrhage into a large abducens nerve schwannoma: a case report
Published in British Journal of Neurosurgery, 2020
Daniel Brown, Nicolas McConnell, Richard List, Farouk Olubajo, Robin Highley, Mathew Storey, Gueorgui Kounin
CT revealed a right pre-pontine cistern mass with areas of central high attenuation. Subsequent MRI (Figure 1) demonstrated the lesion was located along the path of the right abducens nerve between the pontomedullary sulcus and an expanded right Dorello’s canal. Superiorly this was laterally displacing the right trigeminal nerve. A nodular enhancing wall was demonstrated with mixed T1 and T2 weighted signal contents centrally, showing regions of susceptibility artefact. Dural thickening extending into the right internal auditory canal abutted the lesion but appeared separate to it, presumably reactive in nature. A pre-operative diagnosis of haemorrhage within the central cystic cavity of an Abducens nerve schwannoma was therefore made.