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  • By Author: Al-Mefty, Ossama x
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Ossama Al-Mefty, H. Louis Harkey, Isam Marawi, Duane E. Haines, Dudley F. Peeler, Harvey I. Wilner, Robert R. Smith, Howard R. Holaday, Joseph L. Haining, William F. Russell, Brent Harrison and Troy H. Middleton

✓ 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.

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Ossama Al-Mefty, Jane E. Kersh, Anupam Routh and Robert R. Smith

✓ Radiation therapy plays an integral part in managing intracranial tumors. While the risk:benefit ratio is considered acceptable for treating malignant tumors, risks of long-term complications of radiotherapy need thorough assessment in adults treated for benign tumors. Many previously reported delayed complications of radiotherapy can be attributed to inappropriate treatment or to the sensitivity of a developing child's brain to radiation.

Medical records, radiological studies, autopsy findings, and follow-up information were reviewed for 58 adult patients (31 men and 27 women) treated between 1958 and 1987 with radiotherapy for benign intracranial tumors. Patient ages at the time of irradiation ranged from 21 to 87 years (mean 47.7 years). The pathology included 46 pituitary adenomas, five meningiomas, four glomus jugulare tumors, two pineal area tumors, and one craniopharyngioma. Average radiation dosage was 4984 cGy (range 3100 to 7012 cGy), given in an average of 27.2 fractions (range 15 to 45 fractions), over a period averaging 46.6 days. The follow-up period ranged from 3 to 31 years (mean 8.1 years). Findings related to tumor recurrence or surgery were excluded.

Twenty-two patients had complications considered to be delayed side effects of radiotherapy. Two patients had visual deterioration developing 3 and 6 years after treatment; six had pituitary dysfunction; and 17 had varying degrees of parenchymal changes of the brain, occurring mostly in the temporal lobes and relating to the frequent presentation of pituitary tumors (two of these also had pituitary dysfunction). One clival tumor, with the radiographic appearance of a meningioma, developed 30 years post-irradiation for acromegaly. This study unveils considerable delayed sequelae of radiotherapy in a series of adult patients receiving what is considered “safe” treatment for benign brain tumors.

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Ossama Al-Mefty, Louis H. Harkey, Troy H. Middleton, Robert R. Smith and John L. Fox

✓ Eighteen cases are presented in which magnetic resonance (MR) imaging demonstrated two types of lesions in patients with cervical spondylotic myelopathy. In the first type, localized spinal cord changes at the level of compression, consistent with myelomalacia, were revealed best with T2-weighted images as high-intensity spinal cord signals. In the second type, lesions consistent with either cystic necrosis or secondary syrinx were noted locally, and/or extending longitudinally up, and/or down inside the spinal cord. These latter lesions were best revealed as low-intensity signals on T1-weighted MR images and as a signal-void sign (moving fluid) on proton-density or T2-weighted MR images.

It is suggested that segmental lesions at the level of the spondylotic bar represent early proton changes from pressure in and around the same zones that evolve into gray-matter enhancement regions shown as “snake-eyes” on delayed computerized tomography (CT) after myelography. The longitudinal lesions are thought to be the same pencil-shaped zones of cystic necrosis evolving into a secondary syrinx in the late stages (and usually found in the anterior portion of the dorsal columns during delayed CT after myelography). As spinal MR imaging continues to improve, these lesions will be demonstrated more clearly within the cord substance.