eMedicine Specialties > Neurology > Movement and Neurodegenerative Diseases

Syringomyelia

Author: Hassan Ahmad Hassan Al-Shatoury, MD, PhD, MHPE, Assistant Professor, Department of Neurosurgery, Suez Canal University; Co-Director, Center of Research and Development in Medical Education and Health Services Suez Canal University Hospital
Coauthor(s): Ayman Ali Galhom, MD, PhD, Lecturer (Associated Professor), Department of Neurosurgery, Suez Canal University Faculty of Medicine, Egypt; Franklin C Wagner, Jr, MD, Former Chief, Division of Spine and Spinal Cord Surgery, Former Professor, Department of Neurosurgery, University of Illinois at Chicago College of Medicine
Contributor Information and Disclosures

Updated: Sep 24, 2008

Introduction

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. The following are types of syringomyelia.

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 is also 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 is usually 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. Surgical decompression can help in some patients with remarkable neurologic deficit.

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 theory¹

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 theory²

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 theory³

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.

The intramedullary pulse pressure theory

The here-proposed intramedullary pulse pressure theory instead suggests that syringomyelia is caused by increased pulse pressure in the spinal cord and that the syrinx consists of extracellular fluid. A new principle is introduced implying that the distending force in the production of syringomyelia is a relative increase in pulse pressure in the spinal cord compared to that in the nearby subarachnoid space. The formation of a syrinx then occurs by the accumulation of extracellular fluid in the distended cord.

Frequency

United States

Estimated prevalence of the disease is about 8.4 cases per 100,000 people.

International

No geographic difference in the prevalence of syringomyelia is known.

Mortality/Morbidity

Assessing treatment results is difficult because of the rarity of syringomyelia, variability of presentation and natural history, and the relatively short follow-up in most studies.

• In one study, half of all patients with syringomyelia were in clinically stable condition for several years.
• Although an older study had suggested that 20% of patients died at an average of 47 years, mortality rates are likely lower in today's patients as a result of surgical interventions and better treatment of complications associated with significant paresis, such as pulmonary embolism.

Race

• Occurrence of syringomyelia in different races is unknown.
• Familial cases have been described.

Sex

• Syringomyelia occurs more frequently in men than in women.

Age

• The disease usually appears in the third or fourth decade of life, with a mean age of onset of 30 years.
• Rarely, syringomyelia may develop in childhood or late adulthood.

Clinical

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 (lower motor neuron) 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 in long-standing cases.
  • 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

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