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The cause of a t r o p h i c motor loss in the u p p e r e x t r e m i t y in cervical spondylosis has been difficult to i n t e r p r e t because of its c o m m o n association with spinal cord s y m p t o m s and the relative absence of sensory loss. There has been a t e n d e n c y to a t t r i b u t e this dissociated m o t o r loss to cystic degeneration in the anterior horns of the cord. However, some cases with extensive u p p e r ext r e m i t y paralysis do n o t present any long t r a c t spinal cord s y m p t o m s . Because of these, the causative p a t h o l o g y has remained in doubt. We recently h a v e h a d t h e opportunity to follow such a case to p o s t m o r t e m examination, where it became clear t h a t the dissociated m o t o r loss was due to i n d e p e n d e n t compression of the m o t o r roots intradurally, not to cord pathology. This s t u d y clarifies some misconceptions concerning this s y n d r o m e a n d seemed worthy of report.

T HE CLINICAL syndrome of nerve root compression by posterolateral herniation of a lower cervical intervertebral disc has been well presented in recent articles by SenmIes and Murphey, 16 Ulmer and Meredith, 2~ Spurling and Scoville, TM Michelsen and Mixter, 13 Bucy and Chenault, 2 Elliott and Kremer, 4 Bradford and Spurling, I Young,21 Eaton} and Murphey and Meade. ~4 It has been brought to attention by these authors that pain which extends from the lower cervical spine over the upper scapula and down the arm, often with associated numb sensation in some part of the hand, commonly is caused by lower cervical disc herniation. Formerly this syndrome has been variously diagnosed as brachial neuritis, radiculitis, fibrositis, myalgia or reflex pain, with focal infection, cervical arthritis, acromial bursitis, cervical rib, scalenus anticus, cardiac or gall bladder disease often suspected in etiology. Now it is necessary to re-evaluate this type of pain and recognize that it more often is due to nerve root compression by herniation of a lower cervical intervertebral disc. Our present state of knowledge of this herniation is at the same stage as that of herniation of a lower lumbar disc ten years ago when the diagnosis of sciatic neuritis was in vogue, with many hypothetical explanations of its cause, now discarded.The cervical spine and the lumbar spine are similar in their mobility, with frequent forward-bending strain placed upon them and occasional fracture or dislocation in these regions from violent force. In the lumbar region heavy weight bearing on a poor mechanical angle with the sacrum is the most important factor in causation of posterolateral herniation of the nucleus pulposus of the 5th, 4th and 3rd lumbar intervertebral discs, in this order of frequency, whereas fracture-dislocation and hypertrophic arthritis occur more frequently in the upper lumbar region. In the cervical spine similar stress and strain frequently lead to narrowing and border hyperostosis of the lower cervical intervertebral discs, commonly seen in roentgenograms, and at this same site fracture-dislocation usually occurs, indicating that this is the site of greatest combined strain in the neck.Recognition that pathology of the lower cervical discs produces nerve root symptoms has antedated recognition of discrete posterolateral cervical disc herniation, just as other pathology in the lumbar spine was previously used to explain nerve root compression symptoms of disc herniation there. Oppenheimer and Turner ~5 have written extensively of what they have 115

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