Posttraumatic Syringomyelia

The pathophysiology is not understood fully (see Causes). Formation of a cavity within the spinal cord is common after traumatic SCI. Factors related to initial cavity formation include liquefaction of intraparenchymal hematoma, ischemia due to tethering, arterial or venous obstruction, release of intracellular lysosomal enzymes and excitatory amino acids, and mechanical damage from cord compression. Cavity formation alone is not considered PTS.

In PTS, cavity formation is followed by enlargement and extension of the cystic cavity. Rostral or caudal cyst extension may occur due to turbulent CSF flow or a "one-way valve" phenomenon that allows CSF into, but not out of, the cyst cavity. Tethering of the spinal cord, which results in impaired CSF circulation around the traumatized segment of spinal cord, occurs as a sequela of bleeding-induced arachnoiditis, scarring, spinal canal stenosis, or kyphotic deformity.

Syringomyelia can be categorized as “communicating” (dilation of the central canal) and “noncommunicating” (eccentrically located within the substance of the spinal cord). Congenital conditions, such as Chiari malformations, are associated with either communicating or noncommunicating syrinxes. However, PTS is generally considered noncommunicating.[8]

The "slosh-and-suck" theory proposes that increased epidural venous flow occurring during activities (eg, coughing, sneezing) that produce effects like the Valsalva maneuver results in increased pressure around the spinal cord, which cannot be dissipated because of disruptions in CSF flow. This pressure may force CSF into the cyst, resulting in expansion and extension.

A model developed by Carpenter et al suggests that a cough or sneeze can produce a pressure wave that would, in turn, give rise to a shocklike elastic jump.[9, 10] According to the model, the elastic jump could create a transient high-pressure region in the spinal cord, resulting in fluid accumulation. However, in an analysis of the model, Elliott et al maintained that the effect of an elastic jump would probably be too weak for fluid accumulation to result and that "the polarity of the pressure differential set up by cough-type impulses opposes the tenets of the elastic-jump hypothesis."[11] The authors conclude that, based on their analysis, cough-based pressure impulses cannot cause syringomyelia.

A study by Krebs et al of 138 patients indicated that complete SCI and patient age over 30 years are risk factors for developing syrinx early (within 5 years of injury). The study also found that in almost 60% of patients with PTS, the cervical spine was involved.[12]

Frequency

United States

Approximately 3-4% of persons with traumatic SCI develop clinically symptomatic PTS (although that rate has also been listed as about 1-7%[12, 13] ). A larger percentage of persons have clinically silent syrinx cavities diagnosed by imaging techniques.

Mortality/Morbidity

Morbidity is associated with weakness, loss of function, and chronic pain. Mortality can occur from involvement of brainstem respiratory centers or surgical complications.

Race

No racial differences are known for development of PTS.

Sex

The incidence of PTS is higher in men due to the increased frequency of SCI in males; however, there is no association of manifestations of the condition with the patient's sex.

Age

Development of PTS can occur at any age, and may begin at any time after traumatic SCI. Cases are reported as early as 1 month or as late as 45 years following injury. The risk of syrinx development within 5 years following traumatic SCI is greater in persons over age 30 years.[12]

Some patients remain clinically stable for long periods of time, despite large syrinx cavities. In other persons, sensorimotor impairment progresses.

Patients should be educated regarding signs and symptoms to look for. These may include subtle changes in pain and with regard to the bowel, the bladder, sexual function, sensory or motor function, and functional abilities.

See the list below:

• Pain is the most commonly reported symptom. Pain may be localized or diffuse and commonly is reported as a dull ache or a burning or stabbing sensation.

• Other symptoms include increased weakness, numbness, increased spasticity, and hyperhidrosis (increased sweating).

• Symptoms often are aggravated by postural change or the effects of the Valsalva maneuver.

• Decreased reflex micturition, progressive orthostasis, autonomic dysreflexia, and relatively painless joint deformity or swelling (Charcot joint) also may be reported. Syringomyelia is the most common cause of Charcot joint in the upper extremity.[14]

See the list below:

• Spasticity often is increased compared to findings noted in prior examinations. Deep tendon reflex changes (either increased or decreased) may be noted compared with findings from prior examinations.

• Ascending sensory level and sensory dissociation (selective loss of pain and temperature sensation) are very sensitive indicators for detecting progressive PTS. Numbness may involve the face if the syrinx has ascended into the brainstem. (See image below.)

  T2-weighted sagittal image of large, multiloculated cervical syrinx extending into brainstem. Patient had preserved functional status.

• Progressive weakness and wasting can occur but may be a late finding.

• Other signs may include a complete or partial Horner syndrome or other evidence of dysautonomia (eg, labile blood pressure, hyperhidrosis).

• Signs may be unilateral because ascension of syrinxes often occurs unilaterally.

Traumatic SCI with tethering of the spinal cord to the dura results in impaired CSF circulation. Incomplete spinal canal decompression may predispose the person to tethering and CSF obstruction. These factors are thought to cause syrinx development.

Research supports the concept that chronic mechanical stress to the spinal cord increases the risk for development of syringomyelia. Spinal instrumentation without decompression is also associated with earlier onset of syringomyelia.

A study by Asan indicated that syringomyelia is a typical later result of a spinal concussion sustained through vertical forces, as based on magnetic resonance imaging (MRI) performed more than 6 months postconcussion.[15]

A study by Yeo et al found that compared with healthy controls, patients with PTS demonstrated significantly lower peak cranial and caudal CSF flow velocities in the spinal subarachnoid space above and below the syrinx, with a significantly shorter caudal flow duration found. The investigators suggested that an association exists between syrinx formation and changes in the CSF flow’s timing.[16]

See the list below:

• Pulmonary function tests, especially vital capacity, should be ordered on any patient with symptoms or suggested respiratory impairment. Serial studies are useful to document and monitor for progression.

• No specific laboratory blood studies have proven useful in the diagnosis or monitoring of PTS.

See the list below:

• Magnetic resonance imaging (MRI), myelography-enhanced computed tomography (CT-myelography), and plain radiography of the spine are useful in the diagnosis and management of PTS.

• MRI is the preferred initial imaging study for the diagnosis of PTS. Most PTS develops around the site of the original spinal cord lesion. T1 and T2 sequences provide differentiation between CSF and normal spinal cord tissue and areas of spinal cord edema, myelomalacia, or gliosis. Serial examinations are necessary to evaluate for changes in cavity size over time; there is a marked lack of correlation between cavity size and severity of clinical symptoms. (See images below.)

  T1-weighted magnetic resonance imaging (MRI) scan of a slender syrinx (arrow) extending from the C5 vertebral level. This syrinx extends beyond the image to an area of spinal cord disruption at the T3 vertebral level.

  Same patient as in image above, with the magnetic resonance imaging (MRI) scan slightly farther down the cervicothoracic region of the spine

• CT-myelography delineates the extent of the syrinx cavity, arachnoid scarring, and tethering of the spinal cord. This study demonstrates the extent of obstruction to CSF flow.

• Radiographs of the spine delineate spinal deformities such as fractures, dislocations, and abnormal spinal kyphotic or lordotic changes. Flexion/extension views assist in evaluation of spinal stability.

• Ultrasonography may be used intraoperatively after laminectomy to visualize syrinx cavities and septations.

See the list below:

• Serial quantitative strength measurements including pinch and grip tests or hand-held myometry are useful in confirming progression of weakness.

• Calculation of the central motor conduction time using motor evoked potentials is useful in monitoring PTS; however, this technique is not widely available.

• Standard electromyographic techniques, including nerve conduction studies, F-wave latencies, and needle electromyography (EMG), are less sensitive and specific in detecting PTS. Needle EMG may demonstrate a variety of abnormalities, including continuous motor unit activity, synchronous motor unit potentials, myokymic discharges, segmental and propriospinal myoclonus, and respiratory synkinesis. However, as these studies are best used to exclude other causes for the person's symptoms.

On pathologic section, cavitation of the gray matter is seen within the spinal cord. This phenomenon may involve the central canal or may be located eccentrically. An inner layer of gliotic tissue usually is present. The gray matter between the dorsal horns and posterior columns often is involved, possibly because of its relative avascularity and lack of connective tissue. Multiple cyst cavities, separated by complete or partial septae, are often present.

Physical Therapy

The focus of physical therapy in patients with syringomyelia should be preservation of range of motion and maintenance of function, including transfers, wheelchair mobility, and gait if applicable. Selection of appropriate assistive devices also is important. The physical therapist (PT) is helpful in monitoring manual muscle strength and joint function. Exercises and other mobilization activities that produce effects like the Valsalva maneuver should be avoided until normal CSF flow has been restored.

Occupational Therapy

The occupational therapist (OT) is helpful in assessing and treating the function of the person in performance of activities of daily living. The OT may perform splinting to maintain functional positions of the upper extremities and prevent contracture formation. Functional splints and other assistive devices can facilitate the performance of self-care tasks. The OT may perform detailed sensory testing of the upper extremities and quantitative pinch and grip strength testing. The PT and OT may work together in the selection of manual or power wheelchairs and seating systems.

See the list below:

• Increased weakness can result in functional loss, including transfers, wheelchair propulsion, gait, or self-care abilities.

• Functional losses, as well as impairments in sensation, predispose the patient to burns or skin breakdown.

• Progressive impairments in respiratory function place patients at risk for atelectasis, pneumonia, or respiratory failure.

• Neuropathic arthropathy (Charcot joint) can occur as a result of lack of protective joint position sense.

Surgery frequently is performed to prevent further syringomyelia expansion and collapse syrinx cavities. Neurologic deterioration, pain, or autonomic dysreflexia may be indications for surgery.[1] No surgical procedure has been uniformly successful in relief of symptoms or resolution of radiographic abnormalities.

Surgical treatment has included simple drainage, a variety of shunting procedures,[2] and decompressive laminectomy with expansion duraplasty.[3, 4, 5, 6, 17] Cordectomy has also been performed.[7] The question of which persons to treat surgically is controversial. Ideally, surgery should be performed on persons with syrinx cavities that are enlarging but are not yet symptomatic or that have become symptomatic only recently. All surgical procedures potentially can cause loss of motor, sensory, reflex, or autonomic function.[18]

• Shunting of syrinx cavities, when performed alone, historically has been complicated by a high rate (up to 50%) of shunt failure or blockage and recurrent cyst expansion.

• Duraplasty/dural grafting and adhesiolysis may be performed with the goal of reestablishing unrestricted subarachnoid CSF flow. An expansile duraplasty is felt by some to be a more physiologic way of treating a tethered spinal cord with associated syringomyelia. A literature review by Ghobrial et al suggested that in adult patients with postinfectious or posttraumatic syringomyelia, arachnolysis, but not CSF diversion, extends the length of time to clinically symptomatic syringomyelia recurrence.[19]

• Percutaneous CT-guided drainage has been performed but rarely is used.

• Fetal neural tissue has been used to treat progressive PTS in cases where other treatments have failed. Successful obliteration of cyst cavities and survival of fetal tissue have been demonstrated in humans.

• Surgical approaches are evolving with the aim of improving long-term success.

A study by Bratelj et al of patients with posttraumatic spinal cord tethering and syringomyelia found that after untethering surgery, with expansion duraplasty and with or without syrinx shunting, the rate of neurologic improvement was 65.9%, while the rate of spasticity and/or neuropathic pain improvement was 50.0%. The investigators stated that “[i]n symptomatic spinal cord tethering and syringomyelia after trauma, surgical untethering with expansion duraplasty provides a promising treatment strategy to recover clinical deterioration in SCI patients.”[20]

See the images below.

This illustration shows a T1-weighted, cervical magnetic resonance imaging (MRI) scan of multiple syrinx cavities (arrows). Note the lowest thin cavity extending into the thoracic spinal cord.

T2-weighted magnetic resonance imaging (MRI) scan (same patient as above) after patient underwent expansile duraplasty. Note dramatic reduction in size of the main syrinx cavity (white).

T1-weighted image demonstrating a large, multiloculated cervical syrinx cavity. This is a recurrent syrinx, having come back despite an attempt at drainage utilizing expansile duraplasty.

Consultation with a neurosurgeon generally is indicated.

Medical therapy is only for symptomatic control. Definitive treatment to date is surgical in nature.

Class Summary

Antispasticity agents are indicated when spasticity interferes with function, causes pain, or interferes with sleep.

Baclofen (Lioresal)

May induce the hyperpolarization of afferent terminals and inhibit both monosynaptic and polysynaptic reflexes at the spinal level.

Class Summary

Although not an FDA-labeled use, TCAs are considered first-line treatment by specialists to treat many types of neuropathic pain. Doses used generally are less than those required to treat depression.

Amitriptyline (Elavil)

Analgesic for certain chronic and neuropathic pain.

Class Summary

Although not an FDA-labeled use, anticonvulsants are used commonly by specialists to treat neuropathic pain. Gabapentin has the advantage of reduced toxicity and side effects.

Gabapentin (Neurontin)

Has anticonvulsant properties and antineuralgic effects; however, the exact mechanism of action is unknown. Structurally related to GABA but does not interact with GABA receptors. Titration to effect can take place over several days (300 mg on day 1, 300 mg bid on day 2, and 300 mg tid on day 3).

Class Summary

Reduce gastrointestinal, salivary, and sudomotor (sweat gland) activity and can alleviate excess sweating in patients with PTS.

Scopolamine (Transderm Scop)

Blocks action of acetylcholine at parasympathetic sites in smooth muscle, secretory glands, and the CNS. Antagonizes histamine and serotonin action.

Transdermal scopolamine may be the most effective agent for motion sickness. Its use in vestibular neuronitis is limited by its slow onset of action.

Anticholinergic activity used in the treatment of nausea but also can inhibit the secretion of saliva and sweat.

Class Summary

May be necessary in patients whose pain is not controlled with other agents. Long-acting agents are preferred for chronic use.

Oxycodone SA (OxyContin)

Indicated for the relief of moderate to severe pain.

The natural history of untreated syringomyelia is variable, with stabilization of symptoms in some persons and slow but persistent progression in others. Some persons continue to demonstrate progression of the condition, despite surgical intervention. The exact percentage of persons with initially asymptomatic syrinx cavities who become symptomatic is not known.

A literature review by Kleindienst et al indicated that in patients who undergo surgery for posttraumatic syringomyelia, pain, sensory function, and motor function may improve in 43%, 49%, and 55% of them, respectively. However, according to the study, pain can worsen and a deterioration of sensory and motor function can occur in 15%, 27%, and 25% of surgical patients, respectively, with almost all individuals suffering a postoperative decline in autonomic function.[21]

Medical professionals should educate the patient with PTS to avoid actions such as straining or Valsalva-type activities that may worsen symptoms. After successful treatment, this precaution may be lifted.