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The spinal cord travels through a hole in the skull known as the foramen magnum and then travels down the spinal canal which is inside the 33 vertebrae. The spinal cord however ends at about the level of the 1st lumbar vertebra. Thereafter the spinal cord becomes the lumbo-sacral nerve roots which are within the lumbo-sacral canal emerging at the appropriate level through holes in the vertebrae called the neural foraminae.
Nerves emerge from the spinal cord and spinal canal at every level from the neck down to the sacral region.
Each of these nerves emerging will have either a motor, sensory or autonomic function.
The organisation of the peripheral nervous system is fairly controlled in the same way as the topographical anatomy of the brain.
For instance, the nerve that emerges at C7, that is at the level of the 7th cervical vertebra, will go to a number of muscles in the arm and also be responsible for the integrity of the triceps reflex. The same comment applies about all the nerves both from a sensory and motor perspective. It is this pattern of abnormality which enables Neurologists to identify exactly where a problem is taking place in the nervous system. It is the crucial question that all Neurologists ask of themselves when assessing a patient. Where in the nervous system is this problem arising?
As an example, if a patient develops sensory symptoms say in a foot, then those symptoms may be as a consequence of the nervous system going wrong anywhere from the peripheral nerves in the foot extending up the nerve root going into the spinal cord and then up the spinal cord before crossing over the spinal cord about two segmental levels above where the nerve enters the cord. It then extends right through the brain stem, that is the back part of the brain, up until the sensory cortex.
If a Neurologist does not ask the question, where in the nervous system is this taking place, then it is actually impossible to determine the nature of the pathology. A common error within negligence cases is exactly this point. Namely a Clinician, not a Neurologist, will have in effect investigated the wrong part of the nervous system or sadly in some cases not even thought about it such that an unacceptable delay takes place in the appropriate diagnosis and conditions get missed.
There is for instance a condition known as a cauda equine syndrome where the nerve roots of the lumbar canal get crushed, usually by a large midline disc, and this is a neurological and neurosurgical emergency and yet every year a number of patients will have this diagnosis missed, leading to permanent paralysis with loss of bladder and bowel function because a simple question was not asked, namely where in the nervous system could this patient’s problems arise. Once the answer is given, then immediate investigation must follow and there will not be such a delay in the diagnosis.