What is Paraplegia and pathology of spinal cord neural injury?

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INTRODUCTION

Paraplegia refer to partial or complete paralysis of all or part of trunk and both lower extremities, resulting from lesions of thoracic or lumbar spinal cord. OR

It is paralysis or weakness of both lower-limbs due to bilateral pyramidal tract lesion, most commonly in the spinal cord (spinal paraplegia), or peripheral nerve disease, or muscular disease and less commonly in the brain stem or the cerebral parasagittal region (cerebral paraplegia).

The commonest spinal injury to be associated with paraplegia is a fracture-dislocation (flexion-rotation injury) of the dorso-lumbar spine. In one article published in October 2007 says that population most at the risk for spinal cord injuries was the working age group engaged in unskilled work.

India has around 2,00,000 individuals with spinal cord injury . Every year 10,000 new case are added. Despite new technology and rehabilitation strategies, the quality of life of this population is not par with global standards. This is partly owing to fact most of them are rural based, living below the poverty line and are unable to afford cost of rehabilitation. Severe impairments might lead to patients being disabled and wheelchair bound.

Causes of Spinal Paraplegia: (this article will mainly focus on spinal paraplegia)

1. Vertebral compression : Fracture or fracture-dislocation of the vertebra, Disc prolapse and spondylosis, Pott's spin, Neoplastic diseases: Primary or metastatic and Deformity of the vertebral column as kyphoscoliosis.

Traumatic causes includes Road traffic accidents, Subluxation of vertebrae, Suicidal attempts (like jumping down a well), Criminal assault (gunshot injury or stab injury), Falls from a height (occupational injury in South India climbing coconut trees or building construction workers), Sports injuries (horse riding, parachuting, gymnastics)

2. Infections: tranverse myelitis,

3. Vascular: Anterior spinal artery occlusion,

4. Congenital: Meningomyelocele

5. Diseases affecting the spinal cord: Multiple sclerosis, syringomyelia, motor neurone disease

6. Tumors:

Extradural e.g. leukaemic deposits, bony tumor, nerve sheath tumor
Extramedullary-intradural e.g. meningioma, neurofibroma,
Intramedullary-Intradural e.g. ependymoma, astrocytoma, hemangioblastoma

Other causes of paraplegia includes Peripheral nerve damage or muscular dystrophy:

Infections (peripheral nerve affected): Guillain Barre Syndrome (GBS), Poliomyelitis or Postpolio syndrome
Hereditary: Hereditary Spastic paraplegia, Spinal muscular atrophy,
Muscular dystrophy: Duchenne muscular dystrophy, Becker's muscular dystrophy, Limb-girdle muscular dystrophy

Causes of Cerebral Paraplegia:

1. Causes in the Parasagittal Region: (area of cortical presentation of L.L.) it includes

· Traumatic e.g. depressed fracture of the vault of the skull, Subdural haematoma.

· Vascular e.g. superior sagittal sinus thrombosis.

· Inflammatory e.g. encephalitis, meningio-encephalitis.

· Neoplastic e.g. parasagittal meningioma.

· Degenerative e.g. cerebral palsy.

2. Causes in the Brain Stem:
Syringobulbia and midline tumors. These lesions arise in the midline and involve the innermost fibers which are those of the lower limbs.

Fig : Impairments of body functions with respect to level of spinal cord injury

PATHOLOGY OF SPINAL CORD NEURAL INJURY

The displaced vertebra may either damage cord, cord along with the nerve roots or the root alone. Damage to neural structures may be:

1] Cord concussion:

disturbance in functional loss without a demonstrable anatomical lesion.
motor paralysis(flaccid), sensory loss and visceral paralysis occur below lesion.
recovery begin within 8 hours, and eventually the patient recovers fully.

2] Cord transection:

cord and surrounding tissue transected.
injury is irreparable and anatomical lesion present.
flaccid paralysis(acute) ----’spinal shock’(24 hours to 6 weeks )----no control from higher centres---- no voluntary control, loss of sensation and autonomic functions, acts as independent structure(below lesion) ----manifest reflex activity at spinal level .
appearance of signs suggestive of reflex cord activity: bulbocavernous sign and plantar reflex, without recovery of motor power or sensation is an indicator of cord transection.
Stages of reflex activity:

1) Paraplegia in extension: spinal cord lesion is incomplete and affects principally the pyramidal tracts. Hypertonia is predominant in extensor muscle group/ anti-gravity muscles (intact vestibulospinal tract). Extensor tone is controlled by medial reticulospinal tracts (extrapyramidal tracts). The tone of spastic lower limbs as indicated in name is increase in the extensor tone.

2) Paraplegia in flexion: When the lesion progresses to complete cord transaction then both pyramidal tracts as well as other descending extrapyramidal spinal pathways are affected. Hypertonia predominates in flexors muscles (flexor withdrawal reflex or mass reflex occurs). This mechanism occurs due to short spinal reflex arcs facilitation. The legs becomes progressively more flexed at knee and hip and stimulus will provoke strong flexor spasms and mass reflexes which are involuntary.

3) Root transection:

spinal nerve root may be damaged alone in injuries of the lumbar spine (cauda equina affected), or in addition to cord lesion, in injuries of the dorsal lumbar spine.
residual motor paralysis is permanent and regeneration is theoretically possible.
a discrepancy between neurological and skeletal level may occur in spinal injuries below D10 level because the root descending from the segment higher than the affected cord level may also be transected, thereby producing higher neurological level than expected.

4] Incomplete lesion: several syndromes have emerged with consistent clinical features

Brown-Sequard syndrome: occur from hemisection of spinal cord and clinical features are asymmetric ----typically by penetrating wounds i.e. gunshot or stab. On ipsilateral side there is loss of sensation in dermatome segment and paralysis of lesion side, clonus, babinski sign positive. Dorsal column involved: loss of proprioception, vibratory sense and kinesthetics sense. On contralateral side there is damage to spinothalamic tracts resulting in loss of sense of pain and temperature. This loss begins several segment below the level of injury.
Anterior cord syndrome: complete paralysis and anaesthesia present but deep pressure and position sense are retained in the lower limb (dorsal sparing) because they are mediated by posterior column with a separate vascular supply from the posterior spinal artery.----Caused due to flexion injuries of cervical spine.
Central cord syndrome: commonest incomplete lesion. There is initial flaccid weakness followed by LMN type of paralysis of upper limbs (as cervical tracts are more centrally located) and UMN or spastic paralysis of lower limb(lumbar and sacral tracts are located more peripherally), with preservation of bladder control and perianal sensation (sacral sparing)---- hyperextension injuries of cervical spine.
Posterior cord syndrome: it is characterised by isolated ipsilateral loss of vibratory, two point discrimination and conscious proprioceptive sensations. There is ipsilateral loss since the ascending fibers have not crossed. It is a rare condition and occurs when tha damage is towards the back of spinal cord.
Sacral sparing: it refers to incomplete lesion in which the most centrally located sacral tracts are spared. Varying level of innervation from sacral segment remain intact. Clinical signs perianal sensation and external anal sphincter contraction.