Trajectory of the hypoglossal nerve in the hypoglossal canal: significance for the transcondylar approach.
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A microanatomical study of the hypoglossal canal and its surrounding area was carried out using dry skulls and cadaveric heads to determine the course of the hypoglossal nerve in the hypoglossal canal, especially the significance for the transcondylar approach. The hypoglossal nerve enters the superomedial part of the hypoglossal canal as two bundles, which then change course abruptly to an anterosuperior direction, and unite as one trunk before exiting the canal. The hypoglossal nerve has an oblique course in the canal rather than being located in the center, and exits through the inferolateral part of the canal. A venous plexus surrounds the entire length of the nerve bundles in the canal. The present results suggest that during drilling the occipital condyle toward the hypoglossal canal from behind, the surgeon does not need to be overly concerned even if some bleeding occurs from the posterolateral edge of the hypoglossal canal. (+info)
Surgical management of syringomyelia-Chiari complex.
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Great variety exists in the indications and techniques recommended for the surgical treatment of syringomyelia-Chiari complex. More recently, magnetic resonance (MR) imaging has increased the frequency of diagnosis of this pathology and offered a unique opportunity to visualize cavities inside the spinal cord as well as their relationship to the cranio-cervical junction. This report presents 18 consecutive adult symptomatic syringomyelia patients with Chiari malformation who underwent foramen magnum decompression and syringosubarachnoid shunting. The principal indication for the surgery was significant progressive neurological deterioration. All patients underwent preoperative and postoperative MRI scans and were studied clinically and radiologically to assess the changes in the syrinx and their neurological picture after surgical intervention. All patients have been followed up for at least 36 months. No operative mortality was encountered; 88.9% of the patients showed improvement of neurological deficits together with radiological improvement and 11.1% of them revealed collapse of the syrinx cavity but no change in neurological status. None of the patients showed further deterioration of neurological function. The experience obtained from this study demonstrates that foramen magnum decompression to free the cerebro-spinal fluid (CSF) pathways combined with a syringosubarachnoid shunt performed at the same operation succeeds in effectively decompressing the syrinx cavity, and follow-up MR images reveal that this collapse is maintained. In view of these facts, we strongly recommend this technique, which seems to be the most rational surgical procedure in the treatment of syringomyelia-Chiari complex. (+info)
Transcondylar fossa approach to treat ventral foramen magnum meningioma--case report.
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A 41-year-old female presented with a meningioma of the craniocervical junction manifesting as tetraparesis and vesicourethral dysfunction. Neuroradiological examinations showed a homogeneous enhanced mass lesion extending from the foramen magnum to the upper aspect of the second vertebral body. The tumor was totally removed via the transcondylar fossa approach, which is one type of the lateral approach. She was discharged without neurological deficits. The transcondylar approach is often utilized for lesions that occupy the ventral portion around the foramen magnum. The transcondylar fossa approach, a variation of the transcondylar approach, is a refined technique which obtains a closely similar surgical working field. Use of the transcondylar fossa approach remains controversial when treating patients with little brain stem dislocation, a small condylar fossa, and a protruding occipital condyle, but the approach can easily be converted to the transcondylar approach. The transcondylar fossa approach could become a standard method to access the craniocervical junction. (+info)
The historical development of dural substitutes and the process of regeneration of dura mater are reviewed. Lyophilised human cadaver dura mater has been implanted intracranially in baboons and the graft shown to be incorporated with vascularisation but with ossification. In the human, lyophilised dura mater used as a dural substitute also becomes a viable tissue but without ossification. A retrospective study of its use in 100 neurosurgical patients showed a low complication rate and it is suggested that there are occasions when the ready availability of lyophilised dura mater, without the need for a further incision, makes it the dural substitute of choice. (+info)
Biometry of the human occipital bone.
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A biometric study of the occipital bone was carried out on 125 dissecting room skulls; it brought out the following points: 1. The occipital squama, despite its dual histological origin, constitutes a stable anatomical structure because its dimensions remain in correlation if the size factor is maintained constant. 2. The parts around the foramen magnum also show 'organic correlations', but these are virtually unrelated to the squama. 3. The pars basilaris is biometrically independent of the squama; it could well be described with, and regarded as an extension of, the body of the sphenoid if it were morphologically separated from the rest of the occipital bone; there is thus good cause to describe in Man a spheno-occipital 'clivus'. 4. The study of the curvatures of the squama shows that fossil Man agrees with present day Man in that when the occipital is rounded, the parietal is not, and the skull is low and elongated. 5. Sexual differences are more easily described than measured. The shape of the occipital condyles has greater value for sex determination than that of the nuchal crests. 6. Attempts were made to estimate cranial capacity from isolated occipital bones, but one had to be content with a fairly large margin of error. Several types of formulae are nevertheless offered to human palaeontologists in the hope that they might satisfy their need to get a rough indication of cranial capacity from occipital material. (+info)
Surgical experience with skull base approaches for foramen magnum meningioma.
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The surgical treatment of patients with foramen magnum meningioma remains challenging. This study evaluated the outcome of this tumor according to the evolution of surgical approaches during the last 29 years. A retrospective analysis of medical records, operative notes, and neuroimages of 492 meningioma cases from 1972 to 2001 identified seven cases of foramen magnum meningioma (1.4%). All patients showed various neurological symptoms corresponding with foramen magnum syndrome. The tumor locations were anterior in five cases and posterior in two. Surgical removal was performed through a transoral approach in one patient, the suboccipital approach in three, and the transcondylar approach in two. Total removal was achieved in all patients, except for one who refused any surgical treatment. The major complications were tetraparesis and lower cranial nerve paresis for tumors in anterior locations, and minor complications for posterior locations. One patient died of atelectasis and pneumonia after a long hospitalization. The transcondylar approach is recommended for anterior locations, and the standard suboccipital approach for posterior locations. (+info)
Peak systolic and diastolic CSF velocity in the foramen magnum in adult patients with Chiari I malformations and in normal control participants.
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BACKGROUND AND PURPOSE: Abnormal flow of CSF through the foramen magnum has been implicated in the pathogenesis of clinical deficits in association with Chiari I malformation. The purpose of this study was to test the hypothesis that peak CSF velocities in the foramen magnum are increased in patients with Chiari I malformations. METHODS: Eight adult patients with symptomatic Chiari I malformations and 10 adult volunteers were studied with cardiac gated, phase-contrast MR imaging in the axial plane at the foramen magnum. The spatial uniformity of flow velocity in the foramen magnum was assessed at 14 time frames within the R-R interval. The velocity in each of the voxels at each of the time frames was calculated, and the peak systolic and diastolic velocities were tabulated for the patients and controls. RESULTS: For the normal volunteers, the CSF velocities in the subarachnoid space were relatively uniform throughout the subarachnoid space at each of the time frames. Peak systolic velocity ranged from 1.2 to 3.3 cm/s, and peak diastolic velocity ranged from 1.6 to 4.5 cm/s. In symptomatic patients with Chiari I, velocities in the foramen magnum did not appear as uniform throughout the subarachnoid space in the phase-contrast images. Peak systolic velocities ranged from 1.8 to 4.8 cm/s, and peak diastolic velocities ranged from 2.5 to 5.3 cm/s. Peak systolic velocity was significantly higher (P =.01) in the patients than in the control volunteers. CONCLUSION: Patients with Chiari I malformations have significant elevations of peak systolic velocity in the CSF in the foramen magnum. (+info)
On the variability of skull shape in German shepherd (Alsatian) puppies.
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In this study the skulls of 32 German shepherd puppies (40-107 days old) were examined. They were divided into three age groups (40-49, 50-69, and 70-107 days) and the variability of their shapes was determined. Some geometrical shapes were drawn by joining the measuring points. Angle measurements were made on these shapes, which comprised the whole skull, neurocranium, and viscerocranium. The skull index was further calculated in order to assess the correlation, if any, of this index with the angle measurements. It was found that the length of the skull increased more than the width, and, accordingly, the skull became narrower and longer with age. Furthermore, the AZP and AZN angles widened with age, while the ZAZ, ZPZ, NcANc, NcPNc, NcBrNc, SwNSw, and SwPSw angles decreased. The decrease in the skull index, which was not proportionate to the age, showed that the zygomatic width did not increase as much compared to the length of the skull. (+info)