Anatomy External Structure:• The spinal cord is a cylindrical elongated structure flattened dorsoventrally, having a length of 42–45 cm. It lies within the vertebral canal extending from the atlas, continuous with the medulla through the foramen magnum, to the level of the 1st and 2nd lumbar vertebra. Here it tapers into the conus medullaris and terminates as the cauda equina.
• The cervical and lumbar enlargements of the spinal cord provide the nerve roots innervating, respectively, the upper and lower limbs.• There are 31 pairs of spinal nerves, each having dorsal sensory and ventral motor roots that exit the cord (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal).• Three protective membranes, the meninges including the dura mater, being the outer layer, then the arachnoid, and the most inner one, the pia, surround the cord .
• Cerebrospinal fluid flows between the arachnoid and pia. Epidural fat is present in the epidural space between the spinal canal and dura mater.
• When clinical myelopathies develop, these various disorders are classically categorized as intramedullary, that is, intrinsic to the cord, or extramedullary, occurring secondary to disorders extrinsic to the cord.• Extramedullary disorders are further subdivided into those with either an intradural extramedullary locus or a purely extradural site of pathology.
Internal Structure:• White matter, consisting of myelinated fibers, surrounds the butterfly or H-shaped gray matter that contains cell bodies and their processes within the cord’s center. These include both primary ascending sensory fibers and descending motor fibers.
Vascular Supply• One anterior and two posterior spinal arteries course the length of the cord supplying the anterior two thirds and posterior one third of the cord, respectively .• Anterior spinal artery supplies the anterior horn, spinothalamic tract, and corticospinal tract.• Posterior spinal artery supplies the dorsal column and dorsal gray matter• Vertebral artery joins the anterior and posterior spinal arteries to supply the cervical cord.• Aortic segmental arteries provide the supply for the remainder of the cord
Spinal Cord Trauma• This is the most widely studied example of complete spinal cord transection and the prototype of other acute transverse lesions (vascular, demyelinative, compressive) giving rise to paraplegia or quadriplegia with sphincteric paralysis and sensory loss below the level of the lesion.• In cases of cervical spondylosis and/or a congenitally narrow canal, an abrupt, forceful extension of the neck can also severely damage the cervical cord
• The immediate effect of an acute transverse lesion is dependent on its level. If at C1–C3, death from respiratory paralysis is immediate.• If it is lower, there is loss of all motor, sensory, autonomic, and sphincteric function below the level of the lesion. Or if at first the loss of function is not complete, edema and other secondary changes makes it so in a few hours.
• The subsequent effects are divided into two stages: the stage of spinal shock and the stage of heightened reflex activity.• Spinal shock is expressed by a loss of all reflex activity below the level of the lesion, an atonic bladder with overflow incontinence, atonic bowel (paralytic ileus), gastric dilatation, and loss of genital reflexes and vasomotor control.
• After 1 to 2 weeks, sometimes longer, spinal flexor reflexes (Babinski signs, flexor spasms of the legs) and then tendon reflexes begin to appear in parts of the body supplied by the intact but disconnected lower spinal cord segments.• Simultaneously, bladder tone and gastric and bowel function begin to recover. Gradually the tendon reflexes become hyperactive, and the bladder becomes spastic (frequency and urgency of urination, small capacity of bladder with automatic emptying).
• The paralyzed legs tend to remain in flexion or, if the cord lesion is not complete, in extension. In the latter case, there may be some return of motor and sensory function below the lesion.• The treatment of spine fracture and dislocation is mainly orthopedic to reduce subluxation, assure fixation of the spine, and by the immediate administration of high doses of corticosteroids
Nontraumatic AcuteTransverse Myelopathies• Compressive: Tumor, Hemorrhage into the spinal cord (hematomyelia) from an arteriovenous malformation or epidural or subdural hemorrhage(e.g from anticoagulant drugs), or venous compression of the lower cord by a dural fistula or AVM , Epidural abscess( more often subacute in evolution), spondylosis, acute disc herniation,…..etc
Cervical Spondylosis with Myelopathy• This is perhaps the most frequently observed myelopathy in general practice. It is essentially a degenerative disease of the middle and lower cervical vertebrae in which some combination of degenerating and bulging disc(s), vertebral and facet joint exostoses, and thickening of the posterior longitudinal and yellow ligaments are often engrafted on a congenitally narrow spinal canal
• it compromises the cervical cord and roots by compression and possibly by reduction of the blood supply.• Clinically, the syndrome consists of a triad of (1) painful, stiff neck with limitation of the range of movement; (2) radicular pain and numbness and reduced reflexes in an arm; and (3) symmetric or asymmetric spastic paraparesis and ataxia with signs of lateral and posterior column affection.
• Diagnosis is made by MRI or CT myelography and by the exclusion of other spinal cord diseases.• The main differential diagnostic considerations are demyelinative disease and subacute combined degeneration and there is a superficial resembance to amyotrophic lateral sclerosis.• Treatment: analgesia, soft collar and surgery
Demyelinative Myelopathy• Among young adults in northern climates, multiple sclerosis is the most frequent cause of symmetric or asymmetric paraparesis with hyperreflexia and sensory ataxia. About one-third of patients with multiple sclerosis, including older adults, exhibit this essentially spinal form of the disease. A history of earlier attacks of neurologic disorder and the presence of nonspinal findings referable to white matter (optic atrophy, nystagmus, internuclear ophthalmoplegia, ataxia) and cerebral white matter lesions on MRI are helpful in diagnosis.
Spinal Cord Tumors1. Intramedullary: are mostly ependymomas, less often astrocytomas2. Extramedullary intradural: are most often neurofibromas or meningiomas3. Extradural tumors usually prove to be metastatic carcinomas, lymphomas, plasmacytomas, or chordomas
• Radicular pain in combination with asymmetric or symmetric sensory and motor tract involvement and variable sphincteric dysfunction, evolving over weeks or months, constitutes the prototypical syndrome.• Some of the ependymomas progress slowly over months or years, whereas the time course of epidural lymphomas and metastatic carcinomas is measured in days or weeks.
• Radicular symptoms are prominent with neurofibromas but may occur also with meningiomas and other tumors. Back pain and percussion tenderness are the usual features of compression by metastatic tumor.• The treatment of most spinal tumors, even the intramedullary ones, is surgical excision with radiation therapy.
Epidural Abscess• Skin infection in the region of the back or a bacteremia may permit seeding of the epidural space or a vertebral body, which in turn gives rise to an osteomyelitis with extension to the epidural space.• Rarely, infection is introduced by a lumbar puncture needle or laminectomy.• Fever and local pain and tenderness in the back, not necessarily confined to the lumbar spine, are followed within a few days by radicular pain and a rapidly progressive paraparesis and sensory loss in the lower parts of the body, with sphincteric paralysis.
• These clinical findings call for immediate investigation with MRI or CT myelography, followed by laminectomy and drainage, and the administration of appropriate antibiotics in high doses.• Laminectomy must be performed before paralysis becomes established if permanent damage to the cord is to be avoided.
Subacute Combined Degeneration (SCD) of the Cord• This is the name applied to the spinal cord disease resulting from a deficiency of cobalamin (vitamin B12)• It begins with symptoms and signs of posterior column disorder (paresthesias of hands and feet, instability of stance and gait, impaired vibratory and position senses), followed after some weeks by a symmetric ataxic paraparesis with either increased or decreased tendon reflexes and Babinski signs
• The spinal cord lesion may precede the macrocytic anemia by months or a year or more, particularly in patients taking folic acid or those with iron deficiency.• A megaloblastic anemia is an important clue to the diagnosis of vitamin B12 deficiency.• Diagnosis is straightforward when vitamin B12 levels are low• In the early and moderate deficiency state, the administration of parenteral vitamin B12 (initially 1000 μg every 1–2 weeks and later monthly) can reverse the disorder.
Syringomyelia• This syndrome is central cavitation of the spinal cord, predominantly cervical, and often of undetermined cause or occurs as a late complication of spinal cord trauma.• Clinically, syringomyelia is distinguished by segmental weakness and atrophy of the hands and arms with loss of tendon reflexes and a segmental loss of sensation of dissociated type (i.e., loss of pain and temperature sense and preservation of the sense of touch and pressure) in a “cape” distribution over the neck, shoulders, and arms.
• Later in the illness there is weakness and ataxia of the legs from involvement of corticospinal tracts and posterior columns. Pain in the neck and arms, kyphoscoliosis, and lower brainstem signs (syringobulbia) are frequently associated.• Tratment is surgery
Ventral (Anterior) Cord Syndrome• With infarction in the territory of the anterior spinal artery (occlusion of the anterior spinal artery itself or, more often, its extraspinal tributaries), damage is limited to the anterior two- thirds of the spinal cord. Tumor invasion and inflammatory myelitis may have a similar effect. There is paraplegia or quadriplegia, bilateral loss of pain and temperature sensation below the lesion, and sparing of posterior column (joint position and vibration) sense.