Biomedical subjects
Publications and source records attributed to O al-Mefty.
Because of extensive interconnections within the auditory pathways, hearing impairment from a central origin is rare. We describe a patient with a large pineal region meningioma in whom hearing loss was the predominant symptom. The patient promptly recovered hearing after the surgical removal of the tumor. The mechanism of this phenomenon is discussed.
Although meningiomas are benign intracranial tumors, their frequency of recurrence after surgery has not been as low as expected. The recurrence rate of meningiomas is clearly related to the degree of tumor removal. Simpson Grade I removal, which entails excising the tumor and its dural and sinus attachments, is associated with the lowest rate of recurrence. To further minimize the recurrence of convexity meningiomas, we removed an additional dural margin of about 2 cm around the tumor (Grade 0 removal). For tumors involving bone, we removed the hyperostotic bone with a healthy margin and pericranium in en bloc resection. Between 1982 and 1992, 37 patients (15 men, 22 women) with an average age of 52.1 years were operated on by the above technique. Nineteen had a follow-up period of more than 5 years. To date, no tumors have recurred and no morbid incidences have occurred with this maneuver. We believe that the recurrence rate of convexity meningiomas can be diminished by including in the resection a margin of dura that might harbor a foci of tumor cells.
Paragangliomas of the skull base, by virtue of their location, locally infiltrative behavior, and vascular nature, are difficult tumors to resect. Surgical removal is especially complicated when intracranial extensions are encountered. Our experience with a one-stage resection of intracranial extensions of glomus tumors in 20 patients is presented. These 20 patients had a total of 29 paragangliomas: 23 glomus jugulare or tympanicum tumors, 5 carotid body tumors, and 1 pterygopalatine lesion. Ten patients had intradural extension; the other 10 had intracranial extradural tumors. The primary complicating treatment factor was the loss of surgical planes in 6 patients with prior surgery and or radiotherapy. The presence of multiple paragangliomas (20%) and catecholamine secretion by the tumors (15%) complicated surgical treatment as well. Surgical morbidity was primarily related to deficits of lower cranial nerves (50%).
A canine model simulating both cervical spondylosis and its results in delayed progressive myelopathy is presented. This model allowed control of compression, an ongoing assessment of neurological deficits, and evaluation using diagnostic images, frequent electrophysiological tests, local blood flow measurements, and postmortem histological examinations. Subclinical cervical cord compression was achieved in 14 dogs by placing a Teflon washer posteriorly and a Teflon screw anteriorly, producing an average of 29% stenosis of the spinal canal. Four dogs undergoing sham operations were designated as controls. Twelve of the animals undergoing compression developed delayed and progressive clinical signs of myelopathy, with a mean latent period to onset of myelopathy of 7 months. Spinal cord blood flow studies using the hydrogen clearance method showed a significant transient increase in blood flow immediately after compression and a decrease before sacrifice. Somatosensory evoked potential studies indicated progressive deterioration during the period of compression. Magnetic resonance images revealed intramedullary changes. Histological studies showed abnormalities overwhelmingly within the gray matter, including changes in vascular morphology, loss of large motor neurons, necrosis, and cavitation. Axonal degeneration and obvious demyelination were rarely seen. The most profound morphological changes occurred at the site of greatest compression. It is proposed that a momentary arrest of microcirculation occurs during extension of the neck because of loss of the reserve space in the compromised spinal canal. This microcirculatory disturbance is predominant in the watershed area of the cord and mainly affects the highly vulnerable anterior horn cells, leading to neuronal death, necrosis, and eventual cavitation at the junction of the dorsal and anterior horns. Additional supportive evidence of this hypothesis was derived from the literature.
Resection of skull base tumors may sometimes result in massive extirpation defects that are not amenable to local tissue closure. Closure of large basicranial defects can be performed with either a myocutaneous, a deepithelialized myocutaneous, or a simple muscle free flap designed from the ample rectus abdominis vascular territory. This free-tissue donor site has abundant and reliable well-vascularized tissue that can easily be customized to seal these tenuous areas. The rectus abdominis muscle and its vascularized territory were used in 18 of 19 consecutive patients at our center to close basicranial ablation defects. Of these, 6 were rectus abdominis muscle flaps, 5 were myocutaneous rectus abdominis flaps, and 7 were deepithelialized rectus abdominis muscle flaps. All free flaps survived. The intracranial space was sealed successfully in all but one patient. This patient underwent reconstruction with a muscle free flap and had a postoperative cerebrospinal fluid leak. This complication could have been avoided by using a deepithelialized myocutaneous flap to obliterate the central dead space with the vascularized subcutaneous fat. Two patients experienced minor wound infections, and one had a subdural abscess that was fully contained by a free flap placed over the duraplasty. One patient had a donor-site hernia. There was no incidence of meningitis. Knowledge of the anatomy of the vascular territory of the deep inferior epigastric vessels can be used judiciously to secure three-dimensional reconstruction of the skull base. The donor site supplies ample tissue for reconstruction and allows individual tailoring for obliteration of geometrically complex extirpation defects in and around the cranial base without the need to reposition the patient.
This case underscores the difficulty of predicting postoperative hearing status from brain stem auditory evoked response (BAER) monitoring when wave I is preserved and all later waves are lost. During an operation involving the base of the skull, sudden and irreversible loss of all BAER waves beyond wave I occurred unilaterally. Wave I was preserved, with reduced amplitude and minimal latency shift. There was no permanent postoperative hearing sensitivity loss or speech discrimination loss.
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Head and neck manifestations of advanced clival tumors result from subtle, yet progressive mass effect or direct involvement of multiple cranial nerves. Misinterpretation of clinical or radiographic findings in these patients may result in inappropriate treatment planning, increased patient morbidity, and probable tumor recurrence. Our combined experience in managing 21 patients with advanced clival tumors has shown that preoperative loss of vision, diplopia, or facial hypesthesia suggests superior parasellar disease. Facial twitching or neurotologic symptoms result from posterior central tumor growth, while inferior extension of disease leads to basal cranial nerve deficits with associated speech, voice, and swallowing dysfunctions. The purpose of this article is to correlate the complex anatomy of the clivus, brainstem, and cranial base and the various neurotologic findings associated with neoplasms in this region. Lateral skull base surgical procedures, based on preoperative clinicoradiographic assessment, will be detailed with particular emphasis on preservation of critical neurovascular structures.
The involvement of the cavernous sinus by malignant tumors has limited their surgical treatment. We report here a successful en bloc resection of an invasive ethmoid carcinoma involving the cavernous sinus in a 46-year-old man. To prepare for surgery on this patient, a cadaver study was performed to investigate the feasibility of en bloc cavernous sinus resection and reconstruction. The preoperative evaluation, operative approach, and postoperative management are presented.
The syndrome of fat embolism is a well-known clinicopathological entity that may appear 2 to 4 days after skeletal trauma; nontraumatic causes have been recognized, however. This report details the fat embolism syndrome occurring in a patient after surgery within the cavernous sinus to remove a dermoid tumor.
Clinoidal meningiomas have distinguishing clinical, radiological, and surgical considerations. They present a surgical challenge and have a notorious rate of recurrence. The best chance of their cure comes through total removal, but the fear of injury to cerebral vessels has led most surgeons to accept subtotal removal. We classify these tumours into three groups according to the presence or absence of an interfacing arachnoid membrane between the tumour and cerebral vessels. The presence or absence of this membrane depends on the origin of the tumour and its relation to the naked carotid segment lying outside the carotid cistern. In Group I, total removal is impossible and results are disappointing. In Groups II and III, total removal is possible and results are good despite arterial encasement by the tumour.
The cavernous sinus is involved either in lesions arising primarily in the sinus or in lesions invading the sinus from surrounding structures. Experience with direct surgery of the cavernous sinus is encouraging, but no conclusive evidence exists concerning the roles of conservative, surgical, and radiological treatments in terms of effectiveness, morbidity, and long-term results. Consequently, management is individualized according to the patient and the lesions. We discuss these factors in patient selection for cavernous sinus surgery.
Surgical access to the clivus and petrous apex remains a formidable challenge. Intradural tumours at the clivus and petroclival area are superbly exposed via the petrosal approach described here. To date, we have operated on 33 patients having benign tumours using this approach. Total removal was achieved in all patients except 3 with meningiomas. There was no mortality, morbidity included 1 patient with hemiparesis and several with cranial nerve deficits.
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The rationale for direct surgery of the cavernous sinus is presented along with a discussion of patient selection and preoperative evaluation. The surgical approaches for exposing the cavernous sinus and microsurgical techniques used to prepare and open the sinus are described. Principles for the management of neuronal and arterial structures within the sinus are stated and references are given for other technical details.
Therapy for thrombo-occlusive disease of the cerebral venous sinuses remains controversial. Although several thrombolytic agents, such as urokinase and anticoagulants, are recommended for treatment, major significant risks include cerebral hemorrhage, especially in patients with venous infarction. Tissue plasminogen activator (tPA) has shown a high affinity for fibrin-bound plasminogen, while exhibiting a low affinity for circulating plasminogen. The purpose of this study was to evaluate this drug for use in cerebral sinus thrombo-occlusive disease. Eleven adult male rabbits were chosen as experimental animals. All animals underwent microsurgical dissection of their major dural venous sinuses. Direct compression was used to form a thrombus within the sinus. The presence of significant venous thrombosis was confirmed radiographically by iohexol sinography. Subsequently, tPA was delivered systemically via the marginal ear vein at a dose of 3000 units/h; the result was total lysis of the clot documented by a sinogram 1 hour after the drug was administered. Postmortem pathological examination confirmed total lysis in seven of eight animals. One animal showed partial retained clot fragments. No significant coagulopathic state was observed. In three control animals, saline was infused without clot lysis. We conclude that tPA is a highly effective agent for the lysis of acute induced venous sinus thrombosis in an experimental model.
During direct surgery of neoplastic and vascular lesions of the cavernous sinus, the intracavernous carotid artery may be injured beyond repair, or its total isolation may be necessary for surgical management of these lesions. The newly developed procedure of a saphenous vein graft bypass of the cavernous carotid artery allows re-establishment of carotid circulation. Patients with poor collateral circulation are at high risk for ischemic complications induced by the prolonged temporary occlusion required to perform the bypass graft. Optimal management of these patients is to perform the venous bypass graft for permanent vascularization while maintaining carotid cerebral circulation through an intraoperative shunt. We studied this procedure in cadavers, and three shunt types were evaluated: the external intrapetrous-supraclinoid shunt (Type A), the internal intrapetrous-supraclinoid shunt (Type B), and the neck internal carotid-supraclinoid shunt (Type C). Anatomical landmarks, techniques, distances, caliber, and materials used are presented. The rationale and candidates for such a procedure are discussed. The specifications of an optimal balloon shunt are presented, and the three procedures are compared.
The various modifications and variations of the cranio-orbital approach have been recently described; the author uses different modifications according to the location, size and extent of the lesion. Some of the prime indications for these modifications are presented herein.