الفهرس 
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Abstract
This work aimed to evaluate the different diagnostic tools in diagnosis and detection of the cases suffering the intervertebral disc disease. As well as, the uses of the patellar reflex for detection a single level thoracolumbar disc herniation. This work also comprised the histopathological and immunohistochemical examination of the herniated disc materials for investigation and elucidation the mechanism of IVD degeneration in dogs. A total one hundred and thirty-seven dogs were included in this dissertation, which were classified in the different studies as the following:
The first study
Forty-six dogs of different breeds were included in this study. The neurological examination and plain radiography were performed for all dogs. Computed tomography (CT), myeography, CT myelography and magnetic resonance imaging (MRI) were performed for 38, 33, 31 and eighteen dogs respectively. The results showed that Miniature Dachshund is the most common breed suffering IVDD (39.13%). C2-3 was the most affected site in the cervical region (13.37%), while L2-3 is considered the highly affected thoracolumbar site (11.4%) followed with T13-L1 and L1-2 (10.23% for each). The accuracy of each tool for determination the site of lesion was calculated. It was54.3 %, 30.4, 65.8%, 84.85%, 100% and 100% for neurological examination, plain radiography, CT, myelography, CT myelography and MRI respectively.Moreover, the accuracy of CT, myelography, CT myelography for detection of the side of lesion were 44.74%, 54.54% and 93.9% respectively.
The second study
The patellar reflex was used in this retrospective study to determine the site of thoracolumbar spinal cord lesion (T3-L3 or L4-L6). The results of neurological examination were compared to the findings of CT myelography. This study was conducted on 21 dogs which were selected from total 26 dogs confirmed had a single thoracolumbar lesion. Results revealed that the accuracy of patellar reflex for localization of the lesion was 71.4%. The accuracy of patellar reflex (normal or hyperreflexic) for localization of lesion to the T3-L3 segment in 15 dogs was 100%, while the accuracy of depressed patellar reflex for localization of lesion to L4-L6 segment in 6 dogs was 0%. The accuracy of patellar reflex for detection the laterality of thoracolumbar lesion was low (33.33%). The results suggested that the patellar reflex is not likely to be a reliable for neurolocalization of thoracolumbar spinal cord lesion in dogs. This is due to the depressed reflex does not always refer to a lesion in L4-L6 spinal cord segment. Moreover, it is not a reliable factor to detect the laterality of thoracolumbar lesion.
The third study
This study included fifty-seven IVD samples that were removed from fifty-four surgically treated dogs. It comprised 17 cervical and 40 thoracolumbar IVDs. The samples were preserved in 10% formalin, and then kept at -80 Co for histopathological examination. Histopathological grading was performed according to the modified Bergknut histological grading system. The histopathological results of seventeen cervical disc samples varied in the degree of degeneration from the 1st grade to 5th grade. It were (41.2%) for grade 4, (29.4%) for grade 3, (17.65%) for grade 2 and(5.9 %) for both of grade 1 and 5. However the degenerative grades of the thoracolumbar disc samples were restricted only to the 4th and 5th gades. It were 26/40 (65%) for the 4th grade and 14/40 (35%) for the 5th grade. The age of dogs was in negative correlation with degree of degeneration of thoracolumbar disc samples (r= - 0.47, P= 0.0025 and CI= 95%), which was not reported in the cervical disc samples. As well as, there was a significant variation in the degree of degeneration between the cervical and thoracolumbar disc samples (P< 0.0001).
The fourth study
The aim of this study is to investigate the expression of NG2 proteoglycan in degenerated IVDs as a way for elucidation of the pathogenesis of IVD degeneration in dogs. The IVD samples were obtained from 16Dachshunds, confirmed had IVD herniation, and underwent for hemilaminectomy. The samples were subjected to histological and immunohistochemical (IHC) examination. The expression of NG2 proteoglycan using IHC was positive in all examined samples.The results showed the expression of NG2 proteoglycan by the degenerated IVDs.