AUTHOR AND EDITOR INFORMATION

Section 1 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• MRI
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• MRI
• Intervention
• Multimedia
• References

Background

Tubular cavitation of the spinal cord, along with associated progressive neurologic symptoms, has long attracted medical interest. An accumulation of cerebrospinal fluid (CSF) can lead to simple distention of the central canal of the spinal cord, lined by ependymal cells (ie, hydromyelia), or it can dissect into the surrounding white matter to form a paracentral cavity, in which case none of the cavity is lined by ependyma (ie, syringomyelia). In many, if not most, cases, both hydromyelia and syringomyelia are present (ie, syringohydromyelia). As the syringomyelic cavity expands, the initial hydromyelic cavity compresses, and the communication between the 2 cavities may atrophy and be lost. The distinction between hydromyelia and syringomyelia may be difficult even after a detailed histologic examination.

In 1973, Barnett et al¹ published a classic article on the etiology of syringomyelia. The authors classified syringohydromyelic cavities into 5 types:

1. Communicating (with the subarachnoid space, usually at the level of the obex at the inferior aspect of the fourth ventricle)
2. Posttraumatic
3. Tumor related
4. Arachnoiditis related
5. Idiopathic

In a study by Milhorat et al,² the intramedullary cavities were classified into communicating, noncommunicating, and atrophic types to conform to the classification of the ventricular enlargements of the brain.

Overall, the etiologies of communicating hydrocephalus include subarachnoid hemorrhage, meningitis, neoplastic seeding of the leptomeninges, and idiopathic causes. A model of the communicating type can be produced by injecting sclerosing agents into the cisterna magna. Obstruction of the basilar subarachnoid cisterns results in symmetric enlargement of the CSF cavities proximal to the blockage, including all 4 cerebral ventricles and the central canal of the spinal cord.

Noncommunicating syringes are subdivided into 6 types, including:

1. Chiari II malformation with hydrocephalus
2. Chiari I malformation without hydrocephalus
3. Extramedullary compressive lesions at the craniocervical junction or along the length of the spinal canal
4. Spinal cord trauma
5. Intramedullary tumors and intraperimedullary infections
6. Multiple sclerosis

Adhesive spinal arachnoiditis may develop postoperatively or after trauma; following pyogenic, tuberculous, or luetic (syphilitic) meningitis; or after bleeding into the subarachnoid space. Atrophic syringes, which occur with myelomalacia (following trauma or infarction), are associated with a reduction in the transverse dimensions of the spinal cord. Atrophic syringes are limited to a discrete area of myelomalacia in a manner similar to the porencephalic cysts that occur in some cases of encephalomalacia.

Other associated findings include Klippel-Feil anomaly, basilar impression, scoliosis, craniovertebral fusion, and hydrocephalus.

Pathophysiology

Considerable attention has been focused on the pathogenesis of syringes occurring with Chiari malformations. Gardner and McMurray³ originally proposed that obstruction of the outlets of the fourth ventricle causes the CSF pulse wave to be directed caudally, producing a "water hammer" effect that dilates the lumen of the central canal.

Williams⁴ wrote that obstructions at the level of the foramen magnum produce a dissociation of pressure between the cranial and spinal CSF compartments. Fluid is "sucked" from the fourth ventricle into the central canal as a consequence of a relatively lower pressure caudal to the blockage. Other authors, while agreeing that a pressure gradient contributes to syrinx formation, have proposed that the CSF enters the central canal from the spinal subarachnoid space through the enlarged Virchow-Robin spaces as a consequence of increased intraspinal pressure. Hydrodynamic theories have been broadly applied to other types of syrinx formation. Valsalva maneuvers, such as sneezing, coughing, and straining, presumably accentuate the phenomenon by producing sudden changes in spinal venous volume and pressure.

The progression of syringomyelia associated with Chiari I malformation was also attributed to the pulsatile action of the cerebellar tonsils⁵; however, the significance of this finding remains unclear, and this does not necessarily correlate with the presence or absence of symptoms. According to a theoretical model of pressure wave propagation in fluid-filled elastic tubes, the increased pulse pressure that may occur in a region of stenosis of the spinal subarachnoid space (an elastic jump) may be another contributory mechanism for the generation of syringes.

Studies using magnetic resonance imaging (MRI) flow techniques have shown that abnormal global intracranial compliance may play an important role in the generation of syringomyelia and may be a useful parameter in estimating the outcome of decompression surgery in patients with Chiari I malformations.

Basal arachnoiditis (chronic meningitis, subarachnoid hemorrhage, idiopathic origin) may be associated with communicating hydrocephalus. The restriction of CSF equilibration has been proposed as the responsible factor.

Extramedullary lesions, such as chronically herniated discs, basilar impression, and intradural masses, may be associated with syringohydromyelia. In most patients, syringes are found at the lower border of the compressed segment of the spinal cord and are separated from the fourth ventricle by a syrinx-free segment. The location of syringes immediately below an extramedullary obstruction raises the possibility that extrinsic compression of the central canal contributes to dilatation of the lumen caudal to the blockage; however, since syringes are occasionally encountered at or above the level of the extramedullary tumors, the precise mechanism of syrinx formation in these cases is unclear.

A distinctive feature of posttraumatic syringes is their tendency to extend rostrally from the level of the injury. Unless there are associated disturbances in the CSF dynamics caused by conditions such as arachnoid scarring or cord tethering, posttraumatic syringes may not be explained by conventional theories. With intramedullary tumors and infections, the most common cause of spinal cord cavitation is cystic degeneration of the primary neoplastic or infectious lesion. The necrotic process tends to begin centrally and can extend rostrally, caudally, or both ways. Factors independent of the tumor (in particular, disturbances of CSF and extracellular fluid flow) are postulated to play major roles in the pathogenesis of syrinx formation associated with intramedullary tumors. The same factors may apply in cases of intramedullary infection.

At least 3 mechanisms have been proposed to account for cases of adhesive spinal arachnoiditis, including vascular compromise, CSF blockage, and fixation of the spinal cord from meningeal scarring. Focal scarring and spinal blockage may obstruct spinal CSF circulation and force CSF into the spinal cord via perivascular spaces. Circumferential fixation of the spinal cord may create an intrinsic negative pressure within the spinal cord, a process that may further promote the accumulation of fluid in the cord.

Frequency

International

• A direct communication between the syrinx cavity and the fourth ventricle via the obex is present in 14% of patients. Distended syringes that do not communicate with the fourth ventricle are present in 65% of patients. The syrinx-free segment between the syrinx and the obex of the fourth ventricle, as reported, has varied in length from a few centimeters to more than 50 cm.
• The Chiari I malformation is a congenital disorder defined by the caudal displacement of the cerebellar tonsils through the foramen magnum and into the cervical spinal canal. Cerebellar tonsillar ectopia is usually considered to be present when the lower border of the tonsils are more than 5 mm below the plane of the foramen magnum, although the remodeling of the inferior margins of the tonsils into a "wedge shape" is a more reliable observation. A small or narrowed posterior fossa may also be a useful observation. The incidence of syringomyelia of any degree with Chiari I malformation has been reported to be 20-70%. Holocord hydromyelic cavities are seen in 30% of patients with Chiari I malformation and associated syringomyelia.
• The incidence of syringomyelia associated with an intramedullary neoplasm has been reported to be 25-58%. Ependymomas and hemangioblastomas are the most common tumor types to be associated with syringes. Astrocytomas tend to demonstrate syringes less often. Patients with von Hippel—Lindau disease and von Recklinghausen disease appear to have a higher predilection for cyst development within the associated neoplasm.
• In cases of spinal trauma, the incidence of syringomyelia above the spinal fracture site is approximately 3-5%. With the longer survival times currently observed in paraplegic and quadriplegic patients, the incidence of posttraumatic syringomyelia is likely to increase in the future.

Sex

Males and females are equally affected.

Age

Syringomyelia is usually encountered in adults but has occasionally occurred in infants. The youngest reported infant was aged 5 weeks.

Anatomy

When exposed at operation or autopsy, the spinal cord appears swollen and tense in the cervical region and may fill the spinal canal. Externally, the spinal cord appears normal, with no leptomeningeal thickening (idiopathic form). The syrinx is filled with a clear fluid that is usually similar in composition to CSF or is yellow with a high protein content.

Clinical Details

Since syringomyelia is associated with many pathogenetic factors, symptoms are apt to vary, and the classic syndrome of muscular atrophy of the upper extremities accompanied by dissociated sensory loss and long tract signs in the lower extremities is encountered infrequently (50%). The dissociated sensory changes typical of syringomyelia include loss of pain and temperature appreciation, with the preservation of touch and joint positions. Approximately 80% of patients complain of stiffness in the legs and weakness in the legs or hands. Pain is present in 50% of patients and often has a radicular component.

Pain and neurologic complaints may be exacerbated by coughing and sneezing. Progressive scoliosis may be encountered and tends to be localized to the upper thoracic spine. Brainstem findings, including nystagmus, dysphagia, and lower nerve palsies, are present in a small number of patients. Neurogenic arthropathy (ie, Charcot joints) is an unusual event and occurs in fewer than 5% of patients with syringomyelia.

Posttraumatic syringomyelia may develop after either severe or relatively minor spinal cord injury. Enlarging posttraumatic syringomyelia is manifested clinically by a progressive neurologic deficit that extends some distance above the initial site of injury. The clinical problem can develop from several months to many years after the initial injury.

Preferred Examination

MRI is the examination of choice.

RADIOGRAPH

Section 3 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• MRI
• Intervention
• Multimedia
• References

Findings

Patients in whom syringomyelia is suggested by clinical criteria should have the diagnosis confirmed by radiographic investigation. Associated congenital anomalies include basilar impression and platybasia, Klippel-Feil deformity, atlanto-occipital fusion, and spina bifida occurring primarily at the C1 vertebra.

Scoliosis, widening of the central spinal canal, and diastematomyelia are additional associated findings. Peripheral neuropathic joints or even neuropathic alteration of the spine itself may develop in long-standing cases of syringomyelia. Scoliosis associated with markedly destructive changes of shoulder joints should prompt a search for syringomyelia. The most common abnormal radiographic musculoskeletal findings are those of joint distention in dislocation, degeneration, and frank joint destruction. An atrophic form with resorption of the proximal humerus is described frequently in syringomyelia. The scoliosis in this category is a progressive change that results from the cord cavitation, associated loss of anterior horn cells, and perispinal muscular imbalance, ultimately leading to scoliosis as a secondary phenomenon.

Degree of Confidence

MRI findings are characteristic, and the diagnosis is straightforward.

CT SCAN

Section 4 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• MRI
• Intervention
• Multimedia
• References

Findings

MRI is the procedure of choice.

MRI

Section 5 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• MRI
• Intervention
• Multimedia
• References

Findings

The advent of MRI has revolutionized the diagnosis and follow-up imaging of syringohydromyelia. Not only is the disorder more common than previously recognized, but it can now be shown to occur in association with a wide variety of congenital and acquired lesions. With the use of MRI, classifying intramedullary cavities according to anatomic and pathologic types is possible.

• A significant number of syringes are found in association with a variety of intraspinal lesions, and the belief that an abnormality of the cervicomedullary junction is almost always present is not correct.


• Most syringes do not communicate with the fourth ventricle. Even syringes that obstruct the cervicomedullary junction tend to be found at some distance below the foramen magnum and are separated from it by a syrinx-free segment of normal spinal cord. Septations within the syrinx cavity are common with more extensive lesions; however, these septa are always incomplete and do not separate one part of a syrinx cavity from another.


• Syringohydromyelic cavities are frequently associated with intramedullary neoplasia. Nontumoral cysts extending into the parenchyma of the surrounding spinal cord are located at the poles of the tumors and do not enhance on intravenous (IV) contrast-enhanced MRI, while cysts within the substance of the tumor are considered intratumoral cysts and typically demonstrate some degree of peripheral contrast enhancement.


• The many MRI findings in syringomyelia associated with adhesive spinal arachnoiditis have been described. The most striking findings include deformity of the cord at the site of adhesive arachnoiditis, poor definition of part of the syrinx wall, a fluid flow void within the syrinx cavity or cavities, and an absence of associated contrast enhancement. Meningeal thickening is a rare finding.


• Fluid flow voids in the syrinx cavity are not differentiating characteristics of syringomyelia and can be seen in cases associated with Chiari malformations, trauma, and adhesive arachnoiditis. Most cavities associated with intramedullary tumors do not demonstrate a flow void, although rare exceptions have been reported.


• The presence of fluid flow voids in syrinx cavities is common (40%), reflecting pulsatile movements of the syrinx fluid. The appearance of these flow voids may vary depending on the imaging parameters used. As proposed by some authors, these dynamic movements may cause syrinx propagation; therefore, the observation of fluid flow voids within a syrinx cavity may have prognostic significance.


• Detection of fluid movement in a posttraumatic spinal cord lesion may alter therapy. The preoperative assessment can be made based on the presence or absence of cyst fluid flow voids on T2-weighted MRI scans. Progressively symptomatic posttraumatic syringes with positive cyst fluid flow voids usually respond favorably to syrinx shunting into the subarachnoid space or into the peritoneum. Detection and removal of the cause of a CSF flow abnormality, such as arachnoid scarring or cord tethering, may produce favorable results.


• Quantitative measurement of oscillating CSF flow in the spinal canal is possible using an optimized MRI flow-sensitive protocol and can detect stenosis-induced velocity changes. Phase contrast flow imaging has now emerged as the technique of choice.


• Obstruction of the foramen magnum in patients with Chiari I malformation causes an abrupt systolic downward displacement of the spinal cord and impairs the recoil of CSF during diastole. These observations may have pathophysiologic implications.


• Cyst fluid flow measurement is a method for direct serial monitoring of patients with syringomyelic cysts. Diastolic and systolic cyst velocities may assist in evaluating the efficacy of surgery.


• Asymptomatic localized hydromyelia has been reported and probably represents the persistence of a fetal configuration of the central canal of the spinal cord. The central canal of the spinal cord is present at birth and normally becomes progressively obliterated. Cadaver studies have shown that it may persist partially or completely. For this reason, an "incidental" syringomyelic cavity may occasionally be encountered in practice.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble movingor straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

Degree of Confidence

Findings are characteristic for the diagnosis of syringomyelia.

INTERVENTION

Section 6 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• MRI
• Intervention
• Multimedia
• References

Since syringomyelia is a complex pathologic disorder, its treatment is multifaceted and includes a variety of surgical options. Effective syrinx decompression has the potential to reverse neurologic deficits caused by raised intramedullary pressure, but it does not affect deficits caused by the pathologic abnormalities of spinal cord cavitation.

Traditional surgical approaches are based on prevailing concepts of syringomyelia pathogenesis. Treatment of communicating syringomyelia and syringes associated with Chiari II malformation with hydrocephalus consists of placing a ventriculoperitoneal shunt. Decompressive surgery, including limited suboccipital craniectomy and C1 laminectomy with duraplasty, is generally considered the procedure of choice in syringes associated with Chiari I malformations. A significant improvement is observed in 50% of patients.

An adjunct surgical approach to treating Chiari I malformation is syrinx shunting. Shunts to the spinal subarachnoid space are less reliable than shunts to the cerebellopontine angle cistern or to the peritoneal cavity. Other forms of treatment remain controversial, such as shunting of the fourth ventricle, plugging of the obex, and excision of the cerebellar tonsils. Patients who come to surgical attention late in the disease course and who have a rapid loss of neurologic function tend to do poorly. Since the time course of the neurologic change is typically long, a follow-up period of less than 5-10 years after surgery is of questionable value in assessing the final response to therapy.

Initial treatment of syringes occurring with extramedullary lesions should consist of surgical excision of the primary lesion and decompression of the blockage/compression.

Posttraumatic syringes can be treated using syringospinal, syringocisternal, or syringoperitoneal shunts. Posttraumatic cystic myelopathy can occur with or without the presence of the tethered cord syndrome. Detection and removal of the cause of a CSF flow abnormality, such as arachnoid scarring and/or cord untethering, with duraplasty to expand the subarachnoid space may be, in some cases, a more physiologically sound approach. In general, patients with posttraumatic syringomyelia respond favorably to surgery.

Treatment of atrophic syringomyelia is limited to relieving symptoms related to the causal lesion. Operative findings that are associated with a more unsatisfactory result include the presence of dense basal cistern or spinal canal arachnoiditis.

MULTIMEDIA

Section 7 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• MRI
• Intervention
• Multimedia
• References

Media file 1:  T1-weighted sagittal MRI scan demonstrates syringomyelia with a Chiari I malformation without hydrocephalus. The syrinx cavity does not communicate with the fourth ventricle and arises immediately caudal to the descended cerebellar tonsils.
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Media type:  MRI

Media file 2:  Corresponding T2-weighted cervical MRI scan of a patient with a Chiari I malformation (same patient as in Image 1). Note the areas of flow void within the syrinx cavity. The flow void in the syrinx cavity is not a distinguishing characteristic of syringomyelia and can be seen in cases associated with Chiari malformations, posttraumatic syringes, and adhesive arachnoiditis. The presence of a cerebrospinal fluid flow void reflects the pulsatile movements of syrinx fluid. Such movements have been proposed as a cause of syrinx propagation, and observation of flow void may have prognostic significance.
	View Full Size Image
Media type:  MRI

Media file 3:  Midsagittal T1-weighted cervical MRI scan of a young man with a posttraumatic syrinx. Note how the syrinx extends rostrally from the level of the injury. The incidence of significant syringomyelia above the spinal fracture site is approximately 3-5%. With longer survival in paraplegic and quadriplegic patients, the incidence of posttraumatic syringomyelia is likely to increase.
	View Full Size Image
Media type:  MRI

Media file 4:  Midsagittal T2-weighted cervical MRI scan (same patient as in Image 3) demonstrates a flow void sign in the center of the posttraumatic syrinx, reflecting pulsatile fluid motion. Detection of cerebrospinal fluid (CSF) movement in a posttraumatic spinal cord lesion may alter therapy. Preoperative distinction can be made based on the presence or absence of the flow void sign on T2-weighted MRI. Symptomatic posttraumatic syringes with positive flow void sign respond favorably to syrinx-subarachnoid shunting.
	View Full Size Image
Media type:  MRI

Media file 5:  Conus ependymoma associated with syringohydromyelia. Gadolinium-enhanced sagittal MRI scan of the thoracolumbar junction demonstrates an enhancing tumor in the conus medullaris. The syrinx extends rostrally into the cervical cord (not shown). MRI studies of syringomyelia should involve the entire cord to exclude associated pathologies and should include intravenous contrast—enhanced MRI studies to exclude tumor.
	View Full Size Image
Media type:  MRI

Media file 6:  Postoperative arachnoiditis with secondary syringomyelia. T1-weighted sagittal MRI scan shows L1 vertebral body wedge fracture, extensive laminectomy, and a large loculated syrinx. Deformity of the cord margins may suggest arachnoiditis. Adhesive spinal arachnoiditis may develop after trauma, infection, subarachnoid hemorrhage, and spinal surgery.
	View Full Size Image
Media type:  MRI

REFERENCES

Section 8 of 8

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• MRI
• Intervention
• Multimedia
• References

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Article Last Updated: May 9, 2007