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Author: Hassan A Al-Shatoury, MD, MSc, Research Fellow, Department of Neurosurgery, University of Illinois at Chicago - Coauthor(s): Franklin C Wagner, Jr, MD, Chief, Division of Spine and Spinal Cord Surgery, Professor, Department of Neurosurgery, University of Illinois at Chicago College of Medicine

 

Background: Syringomyelia is the development of a fluid-filled cavity or syrinx within the spinal cord. Hydromyelia is a dilatation of the central canal by cerebrospinal fluid (CSF) and may be included within the definition of syringomyelia. Types of syringomyelia include the following:

Syringomyelia with fourth ventricle communication

About 10% of syringomyelia cases are of this type. This communication can be observed on MRI. In some cases, a blockage of CSF circulation occurs. A shunt operation may be the best therapeutic option for these patients.

Syringomyelia due to blockage of CSF circulation (without fourth ventricular communication)

Representing at least 50% of all cases, this is the most common type of syringomyelia. Obstruction of CSF circulation from the basal posterior fossa to the caudal space may cause syringomyelia of this type. The most common example is Arnold-Chiari malformation, which also is associated with communicating syringomyelia. Other causes include the following:

  • Basal arachnoiditis (postinfectious, inflammatory, postirradiation, blood in subarachnoid space)

  • Basilar impression or invagination

  • Meningeal carcinomatosis

  • Pathological masses (arachnoid cysts, rheumatoid arthritis pannus, occipital encephalocele, tumors)

Syringomyelia due to spinal cord injury

Fewer than 10% of syringomyelia cases are of this type. Mechanisms of injury include (1) spinal trauma, (2) radiation necrosis, (3) hemorrhage from aneurysm rupture or arteriovenous malformation or in a tumor bed, (4) infection (spinal abscess, human immunodeficiency virus, transverse myelitis), and (5) cavitation following ischemic injury or degenerative disease.

Syringomyelia and spinal dysraphism

Spinal dysraphism may cause syringomyelia through a variety of mechanisms, including those mentioned under the previous 3 categories. Identification and treatment of associated dysraphism has the greatest impact on arresting progression of syringomyelia.

Syringomyelia due to intramedullary tumors

Fluid accumulation usually is caused by secretion from neoplastic cells or hemorrhage. The tumors most often associated with syringomyelia are ependymoma and hemangioblastoma. Extramedullary intradural and extradural tumors are considered separately under the second category because the mechanism of syrinx formation is blockage of the CSF pathway.

Idiopathic syringomyelia

Idiopathic syringomyelia has an unknown cause and cannot be classified under any of the previous categories.

Pathophysiology: Although many mechanisms for syrinx formation have been postulated, the exact pathogenesis is still unknown. Frequently cited theories are those of Gardner, William, and Oldfield.

Gardner's hydrodynamic theory

This theory proposes that syringomyelia results from a “water hammer”-like transmission of pulsatile CSF pressure via a communication between the fourth ventricle and the central canal of the spinal cord through the obex. A blockage of the foramen of Magendie initiates this process.

William’s theory

This theory proposes that syrinx development, particularly in patients with Chiari malformation, follows a differential between intracranial pressure and spinal pressure caused by a valvelike action at the foramen magnum. The increase in subarachnoid fluid pressure from increased venous pressure during coughing or Valsalva maneuvers is localized to the intracranial compartment.

The hindbrain malformation prevents the increased CSF pressure from dissipating caudally. During Valsalva, a progressive increase in cisterna magna pressure occurs simultaneously with a decrease in spinal subarachnoid pressure. This craniospinal pressure gradient draws CSF caudally into the syrinx.

Oldfield’s theory

Downward movement of the cerebellar tonsils during systole can be visualized with dynamic MRI. This oscillation creates a piston effect in the spinal subarachnoid space that acts on the surface of the spinal cord and forces CSF through the perivascular and interstitial spaces into the syrinx raising intramedullary pressure. Signs and symptoms of neurological dysfunction that appear with distension of the syrinx are due to compression of long tracts, neurons, and microcirculation. Symptoms referable to raised intramedullary pressure are potentially reversible by syrinx decompression.

History: Syringomyelia usually progresses slowly; the course may extend over many years. The condition may have a more acute course, especially when the brain stem is affected (ie, syringobulbia). Syringomyelia usually involves the cervical area. Symptomatic presentation depends primarily on the location of the lesion within the neuraxis. Clinical manifestations include the following:

  • Sensory

    • Dissociated sensory loss: Syrinx interrupts the decussating spinothalamic fibers that mediate pain and temperature sensibility, resulting in loss of these sensations, while light touch, vibration, and position senses are preserved.

    • When the cavity enlarges to involve the posterior columns, position and vibration senses in the feet are lost; astereognosis may be noted in the hands.

    • Pain and temperature sensation may be impaired in either or both arms, or in a shawllike distribution across the shoulders and upper torso anteriorly and posteriorly.

    • Dysesthetic pain, a common complaint in syringomyelia, usually involves the neck and shoulders, but may follow a radicular distribution in the arms or trunk. The discomfort, which is sometimes experienced early in the course of the disease, generally is deep and aching and can be severe.

  • Motor

    • Syrinx extension into the anterior horns of the spinal cord damages motor neurons and causes diffuse muscle atrophy that begins in the hands and progresses proximally to include the forearms and shoulder girdles. Clawhand may develop.

    • Respiratory insufficiency, which usually is related to changes in position, may occur.

  • Autonomic
    • Impaired bowel and bladder functions usually occur as a late manifestation.
    • Sexual dysfunction may develop.
    • Horner syndrome may appear, reflecting damage to the sympathetic neurons in the intermediolateral cell column.
  • Extension of the syrinx
    • A syrinx may extend into the medulla, producing a syringobulbia. This syndrome is characterized by dysphagia, nystagmus, pharyngeal and palatal weakness, asymmetric weakness and atrophy of the tongue, and sensory loss involving primarily pain and temperature senses in the distribution of the trigeminal nerve.
    • Rarely, the syrinx cavity can extend beyond the medulla in the brain stem into the centrum semiovale (syringocephalus).
    • Lumbar syringomyelia can occur and is characterized by atrophy of the proximal and distal leg muscles with dissociated sensory loss in the lumbar and sacral dermatomes. Lower limb reflexes are reduced or absent. Impairment of sphincter function is common.
  • Other manifestations
    • Painless ulcers of the hands are frequent. Edema and hyperhydrosis can be due to interruption of central autonomic pathways.
    • Neurogenic arthropathies (Charcot joints) may affect the shoulder, elbow, or wrist. Scoliosis is seen sometimes.
    • Acute painful enlargement of the shoulder is associated with destruction of the head of the humerus.

Physical:

  • Arm reflexes are diminished early in the clinical course.

  • Lower limb spasticity, which may be asymmetrical, appears with other long-tract signs such as paraparesis, hyperreflexia, and extensor plantar responses.

  • Rectal examination includes an evaluation of volitional sphincter control and sensory assessment of sacral dermatomes.

  • Dissociated sensory impairment may be noted.

  • The syrinx may extend into the brain stem, affecting cranial nerves or cerebellar function.

  • Brainstem signs are common in syringomyelia associated with Chiari malformations.

Causes: Etiology of syringomyelia often is associated with craniovertebral junction abnormalities.

  • Bony abnormalities
    • Small posterior fossa
    • Platybasia and basilar invagination
    • Assimilation of the atlas
  • Soft-tissue masses of abnormal nature
    • Tumors (eg, meningioma at foramen magnum)
    • Inflammatory masses
  • Neural tissue
    • Cerebellar tonsils and vermis herniation
    • Chiari malformation
  • Membranous abnormalities
    • Arachnoid cysts, rhombic roof, or vascularized membranes
    • Posthemorrhagic or postinflammatory membranes
  • Other etiologies not associated with craniovertebral abnormalities
    • Arachnoid scarring related to spinal trauma
    • Arachnoid scarring related to meningeal inflammation
    • Arachnoid scarring related to surgical trauma
    • Subarachnoid space stenosis due to spinal neoplasm or vascular malformation
    • Subarachnoid space stenosis, with possible scarring, related to disk and osteophytic disease
    • Idiopathic

Other Problems to be Considered:

Arnold-Chiari malformations
Cervical rib
Craniovertebral junction anomalies
Increased intracranial pressure
Intrinsic tumors of the spinal cord
Brainstem syndromes
Cervical disk syndromes

Medical Care:

  • No medical treatment is known for patients with syringomyelia. However, a chronic, stable clinical course is common. Identifying the underlying cause of syrinx formation is very important. Surgical treatment most likely will be necessary.
  • Neurorehabilitative care facilitates preservation of remaining neurological functions and prevents complications of quadriparesis such as infection and decubitus ulcers.

Surgical Care: A variety of surgical treatments have been proposed for syringomyelia.

  • Suboccipital and cervical decompression
    • This operation includes suboccipital craniectomy; laminectomy of C1, C2, and sometimes C3; and duraplasty.
    • Some authors report microsurgical lysis of any adhesions, opening of the fourth ventricular outlet, and plugging of the obex (later steps are based on Gardner’s hydrodynamic theory).
  • Laminectomy and syringotomy (dorsolateral myelotomy)
    • After decompression, the syrinx is drained into the subarachnoid space through a longitudinal incision in the dorsal root entry zone (between the lateral and posterior columns), usually at the level of C2-C3.
    • Incision in the dorsal root entry area has the minimum risk of increasing neurological deficit.
  • Shunts
    • Ventriculoperitoneal shunt - Indicated if ventriculomegaly and increased intracranial pressure are present
    • Lumboperitoneal shunt - Placed infrequently because of increased risk of herniation through the foramen magnum
    • Syringosubarachnoid dorsal root entry zone shunt
    • Syringoperitoneal shunt
  • Fourth ventriculostomy

     

  • Percutaneous needling: This technique is advocated as a possible mode of therapy; however, rapid refilling of the hydromyelic cavity from the ventricular system follows aspiration of fluid at the time of surgery. Moreover, a needle track seems unlikely to remain open.

     

  • Terminal ventriculostomy
    • The terminal ventricle is the dilated portion of the central canal that extends below the tip of the conus medullaris into the filum terminale. A laminectomy is performed over the caudal limit of the fluid sac, and the filum is opened.
    • This procedure is suitable only in patients with symptoms of syrinx without Chiari malformation. It is inappropriate in cases in which the hydromyelic cavity does not extend into the lumbar portion of the spinal cord or into the filum terminale.
  • Neuroendoscopic surgery
    • A fibroscope inserted through a small myelotomy allows inspection of the intramedullary cavity.
    • This technique is particularly useful in evaluating and treating multiple septate syrinxes.
    • Septa are fenestrated, either mechanically or by laser. Fluid from the cavity is then shunted into the subarachnoid space.

Consultations:

  • Neurosurgeon

  • Psychiatrist

  • Urologist

  • Physical therapist

  • Occupational therapist

  • Recreational therapist

Diet: No specific diet is recommended for syringomyelia; however, normalizing weight is encouraged, especially in patients with neurological deficits.

Further Inpatient Care:
 

  • Generally, patients with uncomplicated syringomyelia who have mild, relatively stable disability may be monitored on an outpatient basis. Patients with severe disability are better served in the hospital.
  • Postoperative care
    • Provide appropriate care of the surgical wound.
    • Check for CSF leakage from tubes exiting the dura.
    • Provide neck collar as needed for patient comfort.
  • Reported postoperative complications include the following:

    • Worsening of neurological deficit

       

    • Low-pressure headache

       

    • Shunt infection or obstruction

  • MRI is recommended during the early postoperative period as a baseline for further studies.

Further Outpatient Care:
 

  • Document the following at each return visit:
    • Healing of the surgical incision
    • New neurological deficits
    • Status of the integument, genitourinary, gastrointestinal, vascular, and respiratory systems
    • Nutrition, affect/mood, activities of daily living, overall disability, and employment potential
  • Laboratory studies
    • Appropriate blood work
    • Urinalysis and assessment of renal function
  • Specialty referrals
    • Physical therapy

       

    • Occupational therapy: An occupational therapist can assist with specific home or work station modifications. Early referral is indicated to minimize further immobility or inactivity.
       
    • Other referrals: The patient’s care should be reviewed by social services, psychologist, recreational therapist, orthopedist, neurologist or neurosurgeon, urologist, or internist, as appropriate.

Complications:
 

  • Myelopathy is the most serious consequence of syringomyelia. The following are 6 grades of disability from myelopathy:
    • Grade 0 - Root signs and symptoms; no evidence of cord involvement
    • Grade I - Signs of cord involvement; normal gait
    • Grade II - Mild gait involvement; employable
    • Grade III - Gait abnormality prevents employment
    • Grade IV - Ambulates only with assistance
    • Grade V - Chairbound or bedridden
  • Complications due to myelopathy include the following:

    • Recurrent pneumonia

    • Paraplegia or quadriplegia

       

    • Decubitus ulcers

       

    • Bowel and urinary dysfunction

Prognosis:
 

  • Prognosis depends on the underlying cause, the magnitude of neurological dysfunction, and the location and extension of the syrinx.
  • Patients presenting with moderate or severe neurological deficits fare much worse than those patients with mild deficits. Patients with central cord syndrome have poor response to treatment.
  • Natural history of syringomyelia still is not well understood. In one study, half of patients were in clinically stable condition for several years and about 20% of all patients died at an average age of 47 years. Early intervention may improve the outcome.

Patient Education:
 

  • Avoid high-impact exercise, such as running and jumping in cases associated with cervical instability.
  • Avoid activities involving Valsalva maneuvers.

 

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