CLINICAL SCENARIO
- A 21 Year old man was involved in head on collision. When removed from his sports car, he complained of loss of sensation and voluntary movements in his lower limbs. There was also impaired ability of upper limb movements, particularly in his hands. The patient was kept warm and immobilized until the ambulance arrived. After examination at the hospital, x-rays of his vertebral columns were taken.
- X-ray reports: Dislocation of c6 vertebra on C7 and a chip fracture of the anterosuperior corner of body of C7.
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- What is the Anatomical basis behind loss of Voluntary control in Lower limb?
- What was the most likely cause of the patient’s paralysis?
- What is the reason for impaired ability of upper limb movements?
- A Pregnant young woman told her friends that she hated the idea of going through the pain of childbirth but that she equally detested the thought of having a general anaesthetic. Is there a specialized local analgesic technique that will provide painless labour ?.
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- A 69yr old man was admitted to the neurology unit complaining of severe discomfort of the lower back. Radiological examination of the lumbar region of the vertebral column revealed significant narrowing of the spinal canal caused by advanced osteoarthritis.
- Muscle fatigue.
- Prolapsed intervertebral disc.
- Torn ligament in the lumbar regions joints.
- Compression of the Cauda equina.
- Bad posture.
- In persons in whom the spinal cord was originally small , significant narrowing of the canal in the lumbar region can lead to neurologic compression of the cauda equina with pain radiating to the back, as in this patient
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- The Spinal cord is one of the most complex yet quite a fascinating part of the nervous system.
- Its complex connections, the development defects, the lesions, and clinical presentation are quite overwhelming and warrants a better understanding of its anatomical and physiological nature.
- Embryology.
- Introduction.
- Characteristic features of Spinal segments.
- Grey Matter.
- Nerve cell groups in grey columns of spinal cord:
- Cells in Anterior column
- Cells in Posterior column
- Cells in Lateral column.
- White Matter
- The ectoderm of a trilaminar staged embryo will thicken at the midline to be called the neural plate.
- This plate depresses to form a neural groove whose ends later fuse to convert it into a neural tube.
- This tube enlarges at the cranial end and remains tubular at the caudal part.
- The cranial part forms the brain. The spinal cord develops from the caudal tubular part of this neural tube.
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- The neural tube differentiates itself into the ependymal, mantle, and marginal layers from inside out. The mantle proliferates rapidly to form the gray matter.
- The axons of the neuron start occupying the marginal zone during the fourth week of gestation. The axons now bundle up to form ascending and descending tracts within the marginal zone, further subdividing this region into anterior, posterior, and lateral white columns.
- The length of the spinal cord and the vertebral column are equal in size up to the third month of fetal life.
- Later the vertebral column develops rapidly in comparison to the spinal cord. Thus the spinal cord ends at a higher level within the vertebral canal.
- It has receded to the third lumbar vertebra at birth and reaches the first lumbar vertebra by puberty. Thus the spinal nerves arise from the spinal cord at a much higher level than their exit outside through the intervertebral foramina.
- The Spinal cord's most important function is to receive, integrate, associate the input, and produce a reflex response.
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- A Central mass of grey matter made up of nerve cells .
- Peripheral mass of white matter made up of fibre tracts.
- Grey matter is H-shaped (or butterfly shaped).
- Transverse grey commissure(TGC)-divides grey matter into symmetrical right and left mass.
- The central canal of the cord passes through the center of the grey commissure.
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- The canal is surrounded by substantia gelatinosa centralis.
- The lateral grey matter is divided into a narrow elongated posterior horn and broad anterior horn.
- The posterior horn extends almost up to the surface of the cord but anterior horn falls short of it.
- In the thoracic segments and upper two lumbar segments (T1 to L2), a triangular projection juts out from the side of the lateral grey mass between the anterior and posterior horns, called the lateral horn.
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Grey matter
- The grey matter of spinal cord consists of :
- nerve cells,
- neuroglia, and
- blood vessels.
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- The white matter of the spinal cord surrounds the central H-shaped mass of grey matter.
- Mainly consists of nerve fibres.
- Large proportion of them being myelinated, giving it a white appearance.
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- The white matter is divide into 3 parts called columns:
- Posterior white column: between the posterior median septum and the posterior horn.
- Lateral white column: between the anterior and posterior horns.
- Anterior white column: between the anterior median fissure and the anterior horn.
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- The Anterior white columns are joined together by the white commissure.
- Each white column is made up of tracts, which are either ascending (sensory) or descending (motor).
- In general, the posterior white column is sensory, the anterior column is motor and lateral column is mixed (i.e., motor as well as sensory).
- Further, the ascending tracts are located towards the periphery and the descending tracts towards the center.
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- Normally there are 3 neurons in an ascending pathway:
- 1st order neuron : peripheral process extends to skin or other tissues and ends as free nerve endings ( receptors ). Cell body is situated in the posterior root ganglion. Central process extends into spinal cord and synapses with the 2nd order neuron.
- 2nd order neuron : the axon crosses to the opposite side and ascend to a higher level of the CNS
- 3rd order neuron : located in the thalamus and passes to sensory region of the cortex
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- A 21 Year old man was involved in head on collision. When removed from his sports car, he complained of loss of sensation and voluntary movements in his lower limbs. There was also impaired ability of upper limb movements, particularly in his hands. The patient was kept warm and immobilized until the ambulance arrived. After examination at the hospital, radiographs of his vertebral columns were taken.
- Radiologist reports: Dislocation of c6 vertebra on C7 and a chip fracture of the anterosuperior corner of body of C7.
Syringomyelia
- A fluid cavity develops near the centre of the spinal cord usually in the cervical segment.
- This leads to destruction of the cord involving central canal and its surrounding area.
- This lesion involves the decussating spinothalamic fibres in the anterior white commissure.
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- Leads to bilateral loss of pain and temperature sensations below the lesion.
- Other sensations carried by the posterior column tracts are preserved.
- Thus this condition results in what is called dissociated sensory loss
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- Hemisection of spinal cord – Brown Sequard syndrome.
- Ipsilateral spastic paralysis.
- Contralateral loss of pain and temperature.
- Ipsilateral loss of consious proprioception and vibration sense.
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- It is a syphilitic degenerative lesion of the posterior white columns and posterior nerve roots.
- Characterised by impairment of proprioceptive sensibility.
- The patient loses the sense of tactile discrimination, vibration, passive movement and appreciation of posture.
- The patient becomes ataxic, particularly if he closes his eyes.
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- The lesions of pyramidal tract above the level of decussation, that is UPPER MOTOR NEURON (UMN) LESION result in the loss of voluntary movements in the opposite half of the body below the level of lesion.
- The muscles are not actually paralysed but the control on the motor neuron supplying them, that is LOWER MOTOR NEURON (LMN) is lost. AS a result the tone of muscles is increased leading to spastic paralysis.