Spinal Cord Disorders

Athena Kostidis

Edward C. Daly

I. DEVELOPMENTAL DISORDERS

Developmental disorders occasionally cause pain or progressive neurologic dysfunction in adults. Others are found incidentally.

A. Chiari’s malformations

are characterized by descent of the cerebellar tonsils by 5 mm beyond the foramen magnum, with downward displacement of the medulla and kinking of the cervical spinal cord. Hydrocephalus, bony abnormalities of the skull base, and syringomyelia in the cervical cord are frequently found. Chiari I malformations (not associated with meningomyelocele) frequently do not manifest themselves until adulthood. Approximately 80% of patients will have syringomyelia.

1. No treatment is warranted if the patient has no symptoms. Cranial nerve signs, a history of sleep apnea, and radiologic evidence of syringomyelia should be sought. Neurologic and radiologic follow-up evaluation is warranted, especially for children and young adults.

2. If the patient has symptoms, decompressive suboccipital craniectomy and upper cervical laminectomy with or without ventricular shunting are required. However, patients may be stratified to a more or less aggressive surgical approach, based on structural features of the cisterna magna, extent of tonsillar descent, presence of a syrinx, and intraoperative ultrasound findings.

Respiratory depression is the most common postoperative complication necessitating close monitoring.
Approximately 50% of patients benefit, 25% have no change, and 25% deteriorate.

B. Spina bifida occulta

is the anomalous development of the posterior neural arch without an extraspinal cyst. The condition is found in 5% of the population. Cutaneous anomalies often overlie the bony defect. Evidence of other lumbosacral anomalies may be found by means of ultrasonography in infants younger than 3 months or by means of MRI in older patients. Dermal sinus tracts can cause recurrent meningitis. Lipomas and dermoids can impinge on the cord or the cauda equina.

1. Dermal sinus tracts are closed to prevent meningitis.

2. Biopsy is indicated for tissue diagnosis of mass lesions.

3. Surgery is indicated for progressive deficits.

C. Tethering of the cord

by adhesions, lipomas, or a tight filum terminale is the most common finding associated with spina bifida occulta. The syndrome often manifests itself after growth spurts or minor trauma. Pain can be the predominant presentation in adults, whereas scoliosis is more common in children. Bladder and bowel symptoms are common in both.

1. Surgery is controversial in the care of children who have no symptoms. Arguments for early prophylactic surgery are strong because symptoms stabilize but rarely are relieved after surgery. Patients should undergo electromyography (EMG) and urodynamic evaluations before a final decision is made.

2. Surgical release stabilizes progression without a marked effect on bladder dysfunction. Results are mixed for the relief of pain. In follow-up care, the possibility of retethering of the spinal cord has to be monitored.

D. Diastematomyelia

is splitting of the spinal cord by a bony or fibrous septum. The anomaly can become evident during growth spurts or minor trauma. Spina bifida occulta often is present. Pain is prominent in adults but not in children.

1. The septum is removed in children in response to expected progression.

E. Platybasia

(upward displacement of the floor of the posterior fossa) and basilar invagination (protrusion of the odontoid through the foramen magnum) decrease the diameter
of the foramen magnum. In adults, these conditions manifest as spastic tetraparesis or lower cranial nerve dysfunction.

1. Surgical options include decompressive suboccipital craniectomy with upper cervical laminectomy.

2. Counseling is indicated for the apparent genetic basis of skull-base disorders.

F. Syringomyelia

is a congenital pericentral cavity of the cervical spinal cord that may extend into the thoracic cord or upward into the medulla (syringobulbia). Most lesions are between C2 and T9. It most frequently occurs in the setting of Chiari I malformation, but other etiologies include Klippel-Feil’s syndrome, tethered spinal cord, postinfectious, postinflammatory, post-traumatic, and spinal neoplasms.

1. Syringomyelia usually manifests itself in adolescence or adulthood. The classic syndrome of upper-extremity weakness and atrophy (often asymmetric) with dissociated sensation in a “cape distribution” is found in 75% of cases. Enlargement of the syrinx can result in Horner’s syndrome and myelopathy. Sleep-related respiratory disturbances are not uncommon, especially in syringobulbia.

2. Although this disorder often is slowly progressive, long periods of stabilization, as well as of acute deterioration, can occur. Neck or arm pain often is a prominent problem among older patients. Scoliosis may be prominent in younger patients.

Surgery may not be indicated if symptoms are minimal or very severe, if symptoms have been present longer than 5 years, or if the cord is of normal size on MRI.
Surgery may be indicated in the presence of mild deficits of short duration, enlargement of the cord on MRI, and predominant symptoms of pain or spasticity.

3. Surgery is indicated in progressive cases.

Results of surgery. The condition of approximately one-third of patients improves, of < one-half stabilizes, and of approximately one-fourth deteriorates.
- Pain and paraparesis show the best responses.
- Sensory loss, lower motor neuron signs, and brainstem findings are the symptoms least likely to be relieved.

II. VITAMIN DEFICIENCIES

A. Vitamin B₁₂ (cobalamin) deficiency

is the most common disorder of the spinal cord for which specific medical therapy exists.

1. Pernicious anemia

is the most common cause of vitamin B₁₂ deficiency and is thought to be an autoimmune disorder affecting all races and both sexes. Antibodies to parietal cells are found in almost 90% of patients, and antibodies to intrinsic factor are found in somewhat more than 60%. Increased clinical suspicion, automated RBC indices, and insidious onset (it takes 5 to 10 years to deplete normal body stores of cobalamin) make the fully developed classic hematologic and neurologic manifestations clinical rarities today.

2. Other causes

of vitamin B₁₂ deficiency include gastrectomy, diseases of the terminal ileum (Crohn’s disease and diverticulosis), and less severe gastric atrophy (causing food-bound malabsorption). Dietary causes, once thought to be uncommon except in vegans and their breast-fed infants, may be an increasing problem among the elderly. Nitrous oxide exposure during anesthesia can result in precipitous neurologic manifestations in patients with “silent” deficiencies or marginal body stores. Nitrous oxide can also be the cause of an insidious myelopathy if abused.

3. Clinical features.

Hematologic features. The classic severe megaloblastic anemia of insidious onset is relatively rare. Approximately 25% of patients have normal hemoglobin values, 25% have normal RBC indices, and 10% to 20% have completely normal CBCs.
Neurologic features. Approximately 25% to 50% of patients with vitamin B₁₂ deficiency have neurologic symptoms or signs at diagnosis. One study showed that 27% of patients were without neurologic problems but had abnormal signs. Most patients
experience leg dysesthesia as the first symptom. Neurologic presentations include the following:
- Polyneuropathy, autonomic disturbances, and decreased visual acuity.
- Subacute combined degeneration of the spinal cord affecting the posterior and lateral columns. T2 hyperintensity in the posterior columns may be apparent on spinal MR.
- Personality changes, dementia, and psychiatric illness, including psychosis.

4. Diagnosis.

In large-scale screening of elderly persons without symptoms, between 10% and 20% may have cobalamin deficiency.

Serum vitamin B₁₂ (cobalamin). The sensitivity, specificity, and accuracy of this commonly used assay are controversial. Patients can have normal levels and cobalamin-responsive neurologic disorders; low levels and nonresponsive deficits; or low levels but no other evidence of deficiency. Despite these severe shortcomings, measurement of cobalamin in the serum is the screening test that is the most widely available. For most patients, serum folate should be measured at the same time. Cobalamin levels in blood are light and temperature sensitive.
The peripheral blood smear should be examined for macroovalocytes and hypersegmentation of neutrophils. It may be abnormal in the absence of clinically significant anemia, although the sensitivity is low in mild vitamin B₁₂ deficiency.
Methylmalonic acid (MMA) (urine and serum) and serum homocysteine (HCYS) accumulate in vitamin B₁₂ deficiency. HCYS level is also elevated in folate deficiency. Assays for these metabolites can be helpful in selected cases. In comparison with serum cobalamin measurement, these assays are characterized by the following:
- Advantages include possibly better sensitivity and specificity.
- Disadvantages are expense and limited availability.
  - Elevated MMA and HCYS levels are found in hypovolemia, renal failure, and inherited disorders.
  - HCYS level is elevated in hypothyroidism, pyridoxine deficiency, and psoriasis.
Intrinsic factor antibody testing is specific but suffers from low sensitivity (<60%). However, its low cost and simplicity make this test useful as an alternative confirmation of pernicious anemia.
Parietal cell antibody testing is sensitive (>90%) but suffers from low specificity. A negative result makes pernicious anemia unlikely.

5. Treatment.

For patients with pernicious anemia, severe deficits, or poor compliance, the usual treatment is cyanocobalamin in the following dosages: 1 mg per day intramuscularly (IM) for 7 to 12 days, then 1 mg per week IM for 3 weeks, and then 1 mg every 1 to 3 months IM for life. Less severe deficiencies can be initially treated with every other day injections for the first week, then weekly injections for the first month. Monthly injection is the standard maintenance regimen and provides the greatest ease of compliance. If longer intervals are used, MMA levels should document adequate treatment and compliance.
The unusual patient with pernicious anemia and a strong aversion to injections may be offered oral therapy after initial cobalamin repletion. Large doses are needed, because only 1% to 3% of cobalamin is absorbed independently of intrinsic factor. Monitoring of cobalamin levels is needed until compliance is assured. The usual dosage is 1 to 2 mg per day by mouth for life. Recent evidence suggests oral therapy is at least as efficacious as parenteral therapy in reversing the clinical and biochemical indicators of vitamin B₁₂ deficiency.
For patients who are compliant, absorb oral vitamin B₁₂ (the results of a standard Schilling test is normal and serum cobalamin level normalizes), have mild deficits, and want to avoid monthly injections, cyanocobalamin can be given at 50 to 1,000 µg per day by mouth for life. Cobalamin or MMA levels or both should document adequacy of the dosing schedule.

6. Prognosis.

Degree of recovery depends on the severity and duration of deficits at diagnosis. Severe deficits or symptoms that have existed for more than 1 year often respond incompletely. Most improvement occurs within 6 to 12 months. If a patient has not
shown some improvement after 3 months, a response is unlikely. Either the diagnosis was in error or a vitamin B₁₂ deficiency was coexistent but not causal (commonly observed in dementia).

7. Therapeutic strategy.

Predicting which neurologic deficits will respond to vitamin B₁₂ is imprecise. Patients with symptoms or signs consistent with vitamin B₁₂ deficiency and laboratory evidence of a possible vitamin B₁₂ deficiency should be given a 6-to 12-month trial of vitamin B₁₂ if other treatable disorders (including folic acid deficiency) have been eliminated.

B. Folic acid deficiency

is not generally appreciated as a cause of neurologic dysfunction similar to that found in vitamin B₁₂ deficiency. As in vitamin B₁₂ deficiency, the neurologic deficits can develop with normal or mildly abnormal hematologic values. The incidence of severe neurologic deficits is lower in folate deficiency than in cobalamin deficiency.

1. Dietary inadequacy

is the most common cause of folate deficiency, especially among the elderly. Pregnancy, alcoholism, generalized malabsorption, antiepileptic medication, chemotherapy, and congenital defects in absorption or one-carbon enzymes are other potential causes.

2. Clinical features.

Instances of dementia, depression, psychosis, polyneuropathy, and subacute combined degeneration of the spinal cord all have been shown to be responsive to folate supplementation. Changes in mental status and higher cortical functions may be the most common presentations in adults.
An association between maternal folate supplementation and prevention of neural tube defects in the offspring has been found. Folate appears to correct a subtle block in one-carbon metabolism rather than replenish a deficiency.

3. Diagnosis.

A low-serum folate level indicates a negative balance and predicts the likelihood of folate deficiency if uncorrected. The serum level is a poor predictor of total body stores. Because RBC folate level is much greater than serum folate level, hemolyzed specimens should be rejected.
RBC folate level indicates body stores during the lifetime of the RBC. The specificity, sensitivity, and usefulness of the value obtained by means of radioassay (the most common technique) are controversial. If both the serum and RBC folate levels are low, ongoing folate deficiency is suggested.
Elevated serum HCYS level with a normal serum MMA level is also a marker of folate deficiency and can be helpful in equivocal cases. Because cobalamin deficiency also elevates HCYS level, MMA has to be measured at the same time to differentiate the two deficiencies.
A search for a gastrointestinal disorder should be undertaken when signs of malabsorption exist or if a dietary cause is not clear. Gastroenterologic referral and jejunal biopsy should be considered. Concurrent vitamin B₁₂ deficiency can cause folate malabsorption and result in low serum and RBC folate levels. (Vitamin B₁₂ deficiency is more likely to elevate serum folate levels consistent with the methylfolate trap hypothesis.)

There is uncertainty concerning the possible epileptogenic properties of folic acid. Folate deficiency should be confirmed with serum HCYS measurement in the care of patients with seizures. Unless severe hematologic or neurologic deficits are present, less aggressive dosing (1 to 2 mg per day) may be best. Normalization of serum HCYS level is necessary to document compliance and to verify adequate treatment.

6. Prognosis

is generally good if treatment is started early. Poor responses in cases of dementia or depression with folate deficiency probably represent the concurrence of two common disorders in the elderly.

C. Vitamin E deficiency

can cause polyneuropathy, myopathy, scotomata, and demyelination within the posterior columns and spinocerebellar tracts of the spinal cord. The ataxia and posterior column manifestations of abetalipoproteinemia, a rare autosomal recessive disorder of lipoprotein metabolism are responsive to vitamin E supplementation. Rare cases of vitamin E deficiency usually manifest as long-standing malabsorption and steatorrhea. An isolated autosomal recessive defect in transport also exists. Reversal of neurologic deficits with vitamin E supplementation is variable but can be dramatic. Because prognosis appears related to duration of symptoms, a high index of symptoms is warranted. Large oral dosages of vitamin E (800 to 3,600 U per day) or semiweekly injections of α-tocopherol have been used.

D. Copper deficiency

can cause a myelopathy marked by a spastic gait and sensory ataxia. An axonal, sensorimotor polyneuropathy frequently coexists. The myelopathy is most pronounced in the cervical cord compared with the thoracic and lumbar segments. It most frequently presents in the fifth and sixth decades and is more common in women. The clinical and radiographic features are often similar to those seen in subacute combined degeneration from B₁₂ deficiency. In fact, the two conditions may coexist. Causes of copper deficiency include prior gastric surgery, malabsorption (e.g., in celiac disease), parenteral feeding deficiency, and excessive zinc intake (as can be seen with use of certain denture creams). However, in many cases, the cause remains unclear. Hematologic manifestations of copper deficiency include anemia or neutropenia. Treatment with copper supplementation may prevent further neurologic deterioration, and variably can improve symptoms. Supplementation is typically oral, at 6 mg per day for 1 week, then 4 mg per day for 1 week and 2 mg per day thereafter.

III. VASCULAR MALFORMATIONS OF THE SPINAL CORD

A. Classification.

Spinal cord vascular malformations can be classified into intramedullary arteriovenous malformations (AVMs), perimedullary AVMs, spinal-dural arteriovenous fistulas, epidural AVMs, paravertebral vascular malformations, vertebral hemangiomas, and complex angiomatosis. Of these, spinal-dural arteriovenous fistulas are the most common, making up about 70% of all lesions, and thus the rest of this section will focus on this entity.

B. Clinical features.

Patients present with a variety of symptoms distal to the malformation, including progressive paraparesis or radiculopathy, sensory impairment, sphincter disturbances, and pain. When hemorrhage occurs within the lesion, it may result in an acute medullary syndrome.

C. Diagnosis.

Most fistulas are located in the mid to lower dorsal spinal cord (T6-T12). Enhanced MRI is the screening modality of choice, but a spinal-dural fistula may escape detection even on high quality MRI. Therefore, selective spinal arteriography is usually indicated.

D. Treatment.

Endovascular embolization can often cure these lesions. Open surgery is indicated if embolization fails. In some patients, a combination of both embolization and open surgery is the best therapeutic option.

E. Prognosis.

Fistulas in the mid to lower thoracic cord respond best to treatment. Motor symptoms tend to improve most (up to two-thirds of patients), followed by pain and sensory disturbances (up to one-third of patients), and finally sphincteric dysfunction, which is seldom reversible.

IV. SPINAL CORD INFARCTION

Although spinal cord infarctions account for only about 1% of all strokes, they are a cause of significant morbidity. Some common etiologies include prolonged episodes of arterial hypotension, surgical procedures, and pathologies affecting the aorta, disk prolapse or herniation, and arteriopathy; however, in some cases, no cause can be identified. Rarely, spinal cord infarction may be a complication of transforaminal cervical epidural steroid injection. In terms of prevention, motor evoked potentials are commonly been used during
aortic surgeries (e.g., during thracoabdominal aortic aneurysm repair) to alert the surgeon to impending spinal cord ischemia, thus reducing the incidence of paraplegia. The neurological symptoms of spinal cord ischemia are referable to the involved artery or segment of the spinal cord. Pain at the level of infarction is also a common finding. Diagnosis is aided by contrast-enhanced MRI. This should include diffusion-weighted imaging as well, as it may take up to 24 hours for ischemic lesions to appear on conventional sequences (Fig. 45.1). Therapeutic interventions include lumbar CSF drainage with or without vasopressor therapy. Treatment is also supportive and focused on the underlying pathology and secondary stroke prevention (patients generally receive an antiplatelet unless there is a contraindication). Unilateral infarcts have a more favorable prognosis; however, prognosis is largely dependent on the severity of the initial deficit. There is some evidence to suggest that intact proprioception at the onset of the deficit also carries a more favorable prognosis.

V. ACUTE SPINAL CORD INJURY

A. Etiology.

The major causes of acute spinal cord injury are motor vehicle accidents, falls, recreational injuries, and acts of violence. Fracture and compromise of the spinal cord (or cauda equina) occur most often at cervical and thoracolumbar levels. Although thoracic fractures are less common, neurologic injury is more common because of the narrowness of the spinal canal.

B. Prevention.

Proper use of passive and active restraints in automobiles and use of helmets by motorcyclists and bicyclists prevent head and spinal injuries. For example, the Think First program, which addresses educational issues for youth in kindergarten through 12th grade and is actively supported by the neurosurgical community, should be embraced by health care providers.

C. Prognosis.

Improvement of even one level can have a dramatic effect on function, especially in cervical cord injuries (Table 45.1). Final neurologic function depends on severity of initial injury, prevention of secondary damage, and successful management of the complications and sequelae of the acute injury and intensive rehabilitation. Neurologic assessment 72 hours after injury according to American Spinal Injury Association guidelines is useful in estimating outcome.

1. Features suggesting a possibility of neurologic improvement are as follows:

Motor or sensory function below neurologic level (incomplete lesion).
Degree to which motor strength is preserved below neurologic level.
Preservation of pinprick response in addition to light touch below neurologic level.
Age < 30 years.
Residual anal sphincter tone.
Relatively well-preserved vertebral alignment.

2. Features suggesting a poor prognosis are as follows:

Absence of residual function (complete lesion).
Hemorrhage or multilevel edema on MRI.

D. Principles of treatment.

1. Immobilization of the spine

at the scene, in transport, and in the emergency department is critical in preventing further damage.

2. ABCs of trauma care;

supplemental oxygen should be provided.

3. Primary survey

of associated damage.

Alteration of sensorium necessitates investigation for accompanying head injury.
Neurologic level may mask the usual symptoms and signs of thoracic, abdominal, pelvic, or extremity injury. More reliance is placed on objective tests.

4. Radiologic evaluation

of level of skeletal injury.

5. Skeletal traction

Only gold members can continue reading. Log In or Register to continue