Syringomyelia

Syringomyelia is a chronic neurological condition characterized by the development of a fluid-filled cavity, or syrinx, within the spinal cord. This cavity disrupts normal spinal cord function, leading to progressive motor, sensory, and autonomic disturbances. Understanding its anatomy, causes, and clinical implications is crucial for accurate diagnosis and effective management.

Definition and Overview

Meaning of Syringomyelia

Syringomyelia refers to the pathological formation of a syrinx, a cystic cavity filled with cerebrospinal fluid (CSF) that develops within the spinal cord parenchyma. The term is derived from the Greek words syrinx meaning “tube” or “pipe” and myelos meaning “marrow” or “spinal cord.” The syrinx may remain localized or extend over several spinal segments, causing destruction and disruption of neural pathways.

Depending on the underlying cause, syringomyelia can occur as an isolated entity or in association with structural abnormalities such as Chiari malformations, spinal cord tumors, trauma, or infection. The clinical presentation varies based on the level and extent of the syrinx, often progressing slowly over several years.

Historical Background

The earliest descriptions of syringomyelia date back to the 19th century, when pathologists first recognized cystic cavities within the spinal cord during autopsies. In 1827, Ollivier d’Angers provided the first detailed clinical and pathological correlation of the disease, coining the term “syringomyelia.” Since then, advances in neuroimaging, particularly magnetic resonance imaging (MRI), have revolutionized the ability to detect and classify syrinx formations in living patients.

Epidemiology

Syringomyelia is considered a relatively uncommon disorder, though its prevalence has increased with the advent of modern imaging techniques. It can affect individuals of all ages but most commonly manifests in early to middle adulthood. The condition shows no strong gender predilection, although some studies suggest a slight male predominance in post-traumatic cases.

• Incidence and prevalence: Estimated prevalence ranges from 8 to 10 per 100,000 individuals, with higher detection rates in populations undergoing evaluation for spinal or craniovertebral anomalies.
• Age and sex distribution: Most cases present between the second and fifth decades of life, with idiopathic and Chiari-associated forms typically diagnosed in younger adults, and post-traumatic forms occurring in older individuals following spinal injury.

Anatomy and Pathophysiology

Normal Anatomy of the Spinal Cord

To understand syringomyelia, it is important to appreciate the normal structure of the spinal cord. The spinal cord extends from the medulla oblongata to the level of the first or second lumbar vertebra and is composed of central gray matter surrounded by peripheral white matter. The central canal, lined by ependymal cells, runs longitudinally through the cord and contains cerebrospinal fluid (CSF).

• Central canal and ependymal lining: The canal is continuous with the fourth ventricle and plays a role in CSF circulation. It may become dilated or obliterated in pathological states.
• White and gray matter organization: The gray matter forms an H-shaped core containing neuronal cell bodies, while the surrounding white matter carries ascending and descending tracts responsible for sensory and motor transmission.

Pathophysiology of Syringomyelia

The hallmark of syringomyelia is the development of a syrinx that gradually expands, compressing surrounding neural tissue. This leads to progressive damage to the spinal cord tracts and the loss of neuronal integrity. Multiple theories have been proposed to explain the mechanisms of syrinx formation and expansion, most of which center around cerebrospinal fluid (CSF) dynamics.

• Formation of syrinx: The syrinx may arise from dilatation of the central canal or from CSF entry into the spinal cord through perivascular spaces following blockage of normal CSF pathways.
• Mechanisms of CSF flow disturbance: Obstruction at the foramen magnum or spinal subarachnoid space causes pulsatile CSF pressure differentials, forcing fluid into the spinal cord substance.
• Hydrodynamic and pressure theories: The Gardner and Williams theories suggest that altered CSF flow due to hindbrain anomalies drives fluid into the central canal, while the “pressure dissociation” model attributes syrinx formation to imbalanced pressures between intracranial and spinal compartments.

Common Locations and Extent of Syrinx Formation

Syringomyelia most frequently affects the cervical and upper thoracic regions of the spinal cord. The syrinx may remain localized or extend longitudinally, sometimes involving the medulla oblongata, a condition known as syringobulbia. The distribution of the syrinx determines the characteristic sensory and motor deficits seen clinically.

• Cervical and upper thoracic segments: These regions are most commonly affected, leading to upper limb weakness, sensory dissociation, and hand muscle atrophy.
• Associated hindbrain malformations: In cases related to Chiari I malformation, the syrinx often communicates with the fourth ventricle or central canal, reflecting disrupted CSF pathways at the craniovertebral junction.

Etiology and Classification

Primary (Idiopathic) Syringomyelia

In some cases, syringomyelia develops without an identifiable underlying cause and is referred to as idiopathic or primary syringomyelia. This form is thought to arise from congenital or developmental abnormalities affecting cerebrospinal fluid (CSF) flow around the spinal cord, even in the absence of overt structural lesions. Idiopathic cases tend to progress slowly and may remain stable for long periods.

Secondary (Acquired) Syringomyelia

Secondary syringomyelia occurs as a consequence of other pathological processes that disrupt normal CSF dynamics or damage the spinal cord. It may develop months or years after the initial insult, and its severity often correlates with the extent of underlying injury or obstruction.

• Post-traumatic: Arises after spinal cord injury, where scar tissue, adhesions, or arachnoiditis obstruct CSF flow. Progressive cavitation within the cord can lead to delayed neurological decline.
• Post-infectious: Results from inflammation or scarring following meningitis or other central nervous system infections, leading to abnormal CSF circulation.
• Tumor-related: Occurs when an intramedullary or extramedullary spinal tumor (such as ependymoma or astrocytoma) obstructs CSF flow or compresses the spinal cord, creating a cavity distal to the lesion.
• Post-inflammatory or post-ischemic: Chronic inflammatory processes or vascular insults may cause necrosis and cavitation within the spinal cord, forming secondary syrinx cavities.

Association with Chiari Malformations

The most common association of syringomyelia is with Chiari type I malformation, in which the cerebellar tonsils herniate downward through the foramen magnum. This herniation impedes normal CSF circulation between the cranial and spinal subarachnoid spaces, resulting in a pressure differential that drives fluid into the spinal cord. Surgical decompression of the foramen magnum often leads to a reduction or resolution of the syrinx.

Classification Based on Pathogenesis and Location

Syringomyelia can be categorized by its origin, communication with the ventricular system, and anatomical location within the spinal cord. These classifications assist in diagnostic interpretation and management planning.

• Communicating syringomyelia: The syrinx communicates directly with the fourth ventricle, usually secondary to congenital malformations such as Chiari I or II anomalies.
• Non-communicating syringomyelia: The cavity does not connect to the ventricular system and typically results from trauma, tumors, or inflammatory lesions.
• Central syrinx: Located along the central canal and often symmetrical in distribution.
• Eccentric syrinx: Lies off-center within the spinal cord and may cause asymmetrical neurological deficits.

Clinical Features

Onset and Progression

Syringomyelia usually has an insidious onset, with symptoms developing gradually over several months or years. The progression can be slow and intermittent, and the disease may remain stable for long periods before worsening. Symptoms typically correspond to the spinal levels involved by the syrinx, most commonly in the cervical and upper thoracic regions.

Motor Symptoms

Motor deficits result from disruption of anterior horn cells and corticospinal tracts within the spinal cord. These lead to weakness, muscle wasting, and altered reflexes that may present in both upper and lower limbs depending on the extent of the lesion.

• Muscle weakness and wasting: Atrophy of the small muscles of the hands and forearms is characteristic, producing a “claw hand” appearance in advanced cases.
• Spasticity and hyperreflexia: Involvement of the corticospinal tracts results in increased tone and exaggerated deep tendon reflexes, particularly in the lower limbs.

Sensory Symptoms

Sensory impairment is one of the hallmark features of syringomyelia, often presenting as a distinct pattern known as “dissociated sensory loss.” This refers to the selective loss of pain and temperature sensations with preservation of touch, vibration, and proprioception.

• Dissociated sensory loss: Caused by damage to the decussating fibers of the spinothalamic tract in the anterior white commissure, leading to bilateral loss of pain and temperature in a cape-like distribution across the shoulders and arms.
• Preservation of touch and proprioception: The posterior columns remain intact, maintaining fine touch and position sense.

Autonomic and Other Features

As the syrinx expands, it may affect autonomic neurons and descending sympathetic pathways, leading to disturbances in sweating, bladder, and sexual function. Skeletal deformities such as scoliosis may also occur, particularly in children and adolescents.

• Loss of sweating: Anhidrosis or patchy hyperhidrosis occurs due to autonomic dysfunction.
• Scoliosis: Results from asymmetrical weakness of paraspinal muscles or growth-related distortion in juvenile cases.
• Bladder and sexual dysfunction: Occurs when sacral autonomic pathways are affected, leading to urinary retention, incontinence, or impotence.

Characteristic Sensory Patterns

The sensory loss in syringomyelia typically presents in a “cape-like” distribution over the back of the neck, shoulders, and arms. In lower spinal involvement, loss may extend to the trunk and legs. This distinctive pattern helps differentiate syringomyelia from other spinal cord pathologies during neurological examination.

Associated Conditions and Syndromes

Syringomyelia rarely occurs in isolation and is frequently associated with other neurological or structural abnormalities of the spinal cord and posterior fossa. Recognition of these associations is crucial for accurate diagnosis and management, as treatment often requires addressing the underlying condition contributing to syrinx formation.

• Chiari type I malformation: The most common condition linked with syringomyelia. It involves downward displacement of the cerebellar tonsils through the foramen magnum, obstructing cerebrospinal fluid (CSF) flow between the cranial and spinal compartments. Surgical decompression of the posterior fossa can often relieve the syrinx.
• Spinal cord tumors: Intramedullary tumors such as ependymomas and astrocytomas may obstruct CSF pathways or directly compress the spinal cord, resulting in secondary syrinx formation. Removal of the tumor often leads to syrinx regression.
• Arachnoiditis and spinal trauma: Scarring of the arachnoid mater following infection, surgery, or trauma can block normal CSF circulation, creating conditions conducive to syrinx development.
• Congenital abnormalities: Conditions such as tethered cord syndrome and spina bifida can alter CSF flow dynamics, leading to chronic cord cavitation.
• Post-inflammatory disorders: Chronic meningitis or granulomatous diseases may lead to adhesive arachnoiditis, a known risk factor for syringomyelia.

Understanding these associated syndromes helps clinicians distinguish between primary and secondary syringomyelia and tailor management accordingly.

Diagnosis

Clinical Evaluation

Diagnosis begins with a detailed clinical history and neurological examination. The pattern of sensory loss, motor weakness, and autonomic dysfunction provides essential clues. A slow, progressive course of bilateral pain and temperature loss with preserved touch strongly suggests syringomyelia.

• History and neurological examination: Key findings include dissociated sensory loss, segmental muscle atrophy, spasticity, and reflex changes. The presence of scoliosis or chronic pain should also prompt evaluation for a syrinx.
• Pattern recognition of deficits: The distribution of symptoms often corresponds to the spinal segments involved by the syrinx, aiding localization before imaging studies are performed.

Imaging Studies

Magnetic resonance imaging (MRI) is the gold standard for diagnosing syringomyelia. It provides high-resolution visualization of the syrinx, associated anomalies, and CSF flow patterns.

• Magnetic Resonance Imaging (MRI): Demonstrates the syrinx cavity as a fluid-filled, elongated lesion within the spinal cord. T1- and T2-weighted images differentiate the syrinx from surrounding tissue, while contrast enhancement may reveal associated tumors or inflammation.
• Cine MRI for CSF flow analysis: Used to assess CSF pulsations at the foramen magnum and around the spinal cord, especially useful in Chiari-associated syringomyelia.
• CT myelography: Serves as an alternative in patients who cannot undergo MRI. It delineates the spinal canal and identifies any obstruction to CSF flow or compressive lesions.

Electrophysiological Studies

These studies help assess the functional integrity of spinal pathways and confirm neurological involvement when imaging findings are equivocal.

• Somatosensory evoked potentials (SSEPs): Detect delayed conduction along sensory tracts, indicating spinal cord dysfunction.
• Motor evoked potentials (MEPs): Evaluate corticospinal tract integrity and may reveal subclinical motor deficits in early syringomyelia.

Differential Diagnosis

Several spinal cord disorders can mimic the presentation of syringomyelia, making differential diagnosis essential to avoid mismanagement.

• Multiple sclerosis: May present with similar sensory and motor symptoms but typically shows disseminated demyelinating plaques on MRI.
• Intramedullary tumors: Produce progressive neurological deficits and may resemble a syrinx on imaging, but often enhance with contrast and cause localized swelling.
• Transverse myelitis: Causes acute spinal cord inflammation with symmetric sensory and motor deficits, unlike the chronic, segmental pattern of syringomyelia.
• Spinal cord infarction: Produces sudden-onset neurological deficits with localized vascular pathology, distinct from the gradual evolution seen in syringomyelia.

Accurate diagnosis requires a combination of clinical acumen and advanced imaging, as early detection is key to preventing irreversible neurological damage.

Complications

Untreated or progressive syringomyelia can lead to a variety of neurological, orthopedic, and autonomic complications that significantly impair quality of life. The severity and distribution of complications depend on the size and level of the syrinx and the degree of spinal cord involvement.

• Progressive neurological deterioration: Ongoing destruction of spinal cord tissue results in worsening motor weakness, atrophy, and spasticity. In advanced cases, paraplegia or quadriplegia may occur.
• Joint deformities (Charcot joints): Loss of pain and temperature sensation predisposes to repetitive trauma and joint degeneration, especially in the shoulders and elbows, leading to neuropathic arthropathy.
• Chronic pain syndromes: Persistent burning or stabbing pain in the neck, shoulders, or limbs may result from disruption of central pain pathways. This can become debilitating and resistant to conventional analgesic therapy.
• Autonomic instability: Damage to sympathetic fibers can cause irregular sweating, blood pressure fluctuations, and abnormal temperature regulation, particularly in lesions involving the upper thoracic cord.
• Scoliosis and skeletal deformities: Asymmetric muscle weakness in children or adolescents may lead to spinal curvature, which can further compromise spinal stability and respiratory function.
• Bladder and bowel dysfunction: Involvement of sacral autonomic pathways leads to urinary retention, incontinence, or constipation, complicating long-term care.

Early recognition and management of these complications are vital to prevent irreversible disability and improve overall functional outcomes.

Treatment and Management

Conservative Management

Conservative therapy is appropriate in cases where the syrinx is small, asymptomatic, or stable on serial imaging. The goal is to minimize symptom progression and preserve neurological function through non-surgical means.

• Observation in stable cases: Regular clinical and radiological follow-up using MRI helps monitor changes in syrinx size or symptom progression. Intervention is reserved for cases showing neurological deterioration.
• Physical therapy and rehabilitation: Targeted exercises maintain muscle strength and joint mobility. Postural training and gait correction reduce stress on weakened musculature and help manage scoliosis.
• Pain management: Neuropathic pain is treated with medications such as gabapentin, pregabalin, or tricyclic antidepressants. In resistant cases, transcutaneous electrical nerve stimulation (TENS) or nerve blocks may be considered.

Surgical Management

Surgery remains the mainstay of treatment for progressive or symptomatic syringomyelia, particularly when the syrinx is associated with obstruction of cerebrospinal fluid (CSF) flow or compressive lesions. The objective of surgery is to restore normal CSF dynamics and decompress the spinal cord.

• Posterior fossa decompression: Performed in patients with Chiari malformation, this procedure enlarges the foramen magnum and relieves tonsillar impaction, allowing reestablishment of CSF flow between the cranial and spinal compartments.
• Syrinx drainage or shunting procedures: Involves insertion of a syringoperitoneal, syringosubarachnoid, or syringopleural shunt to divert fluid from the syrinx cavity. This may be indicated in post-traumatic or idiopathic cases.
• Correction of CSF flow obstruction: In cases secondary to arachnoid adhesions or fibrosis, lysis of adhesions or reconstruction of subarachnoid pathways may help restore normal CSF circulation.
• Tumor resection in secondary syringomyelia: When syringomyelia is caused by an intramedullary tumor, surgical excision of the mass often results in collapse or resolution of the syrinx.

Postoperative Care and Follow-up

Postoperative management involves close neurological monitoring, physiotherapy, and serial MRI evaluations to ensure syrinx reduction and prevent recurrence. Patients may require long-term rehabilitation for residual deficits and chronic pain management. Recurrence of the syrinx, although uncommon, necessitates reassessment of CSF flow and possible surgical revision.

A multidisciplinary approach combining neurosurgery, neurology, and rehabilitation medicine offers the best outcomes for individuals with syringomyelia. Early intervention and continuous follow-up remain critical to preserving neurological function and improving quality of life.

Prognosis

The prognosis of syringomyelia varies widely depending on its underlying cause, the extent of spinal cord involvement, and the timing of diagnosis and intervention. Early recognition and appropriate management can significantly improve neurological outcomes and prevent irreversible deficits.

• Factors influencing outcome: Patients with smaller syrinx cavities and limited neurological impairment tend to have better outcomes than those with extensive cavitation or long-standing symptoms. Surgical decompression for Chiari-associated syringomyelia often leads to stabilization or regression of the syrinx and improvement in pain and motor function.
• Effect of treatment timing: Delayed treatment increases the risk of permanent damage to spinal tracts and anterior horn cells, leading to persistent weakness, sensory deficits, and autonomic dysfunction.
• Recurrence and long-term management: In some cases, syringomyelia may recur due to re-obstruction of cerebrospinal fluid (CSF) pathways or shunt malfunction. Periodic follow-up with MRI is essential to detect recurrence early and initiate corrective measures.
• Functional recovery: Rehabilitation following surgery plays a crucial role in restoring mobility and independence. Pain control, muscle strengthening, and adaptive training help improve the patient’s daily functioning and overall quality of life.

Although syringomyelia remains a chronic condition in many cases, timely diagnosis and intervention can significantly reduce disability and enhance long-term outcomes.

Recent Advances and Research

Recent advances in diagnostic imaging, neurosurgical techniques, and neurophysiological research have greatly improved understanding and management of syringomyelia. Ongoing studies continue to explore the molecular and biomechanical mechanisms underlying syrinx formation, with the aim of developing more effective treatments.

• CSF flow dynamics and hydrodynamic modeling: Advanced computational models and cine phase-contrast MRI techniques are now used to analyze CSF pulsations and pressure gradients at the foramen magnum and spinal canal. These studies have enhanced the understanding of syrinx expansion and guided individualized surgical planning.
• Advances in microsurgical and endoscopic techniques: Minimally invasive approaches for posterior fossa decompression and shunt placement have reduced postoperative morbidity and improved precision in restoring CSF flow.
• Intraoperative neuromonitoring: The use of somatosensory and motor evoked potential monitoring during surgery helps prevent iatrogenic injury and optimizes neurological preservation.
• Neuroprotective and regenerative therapies: Experimental research is investigating agents that reduce spinal cord inflammation and promote neural regeneration. Stem cell therapy and biomaterial scaffolds hold promise for future treatment of post-traumatic syringomyelia.
• Long-term imaging follow-up: High-resolution MRI and diffusion tensor imaging (DTI) are increasingly used to evaluate spinal cord microstructure, monitor treatment response, and detect subclinical changes.

These developments represent a shift toward more personalized and minimally invasive management strategies. As understanding of CSF physiology and neural repair continues to advance, the prognosis for patients with syringomyelia is expected to improve substantially in the coming years.

References

1. Standring S, ed. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. Elsevier; 2021.
2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 9th ed. Wolters Kluwer; 2023.
3. Williams B. On the pathogenesis of syringomyelia: A review. J Neurol Neurosurg Psychiatry. 1980;43(2):137-149.
4. Milhorat TH, Kotzen RM, Anzil AP. Stenosis of central canal of spinal cord in man: Incidence and pathological findings in 232 autopsy cases. J Neurosurg. 1994;80(4):716-722.
5. Ball MJ, Day JD. Pathophysiology and management of syringomyelia associated with Chiari malformation. Neurosurg Clin N Am. 2015;26(4):533-540.
6. Heiss JD, Patronas N, DeVroom HL, et al. Elucidating the pathophysiology of syringomyelia. J Neurosurg. 1999;91(4):553-562.
7. Koyanagi I, Houkin K. Pathogenesis of syringomyelia associated with Chiari type I malformation: Review of evidence and proposed hypotheses. Neurosurg Focus. 2000;8(3):1-9.
8. Royo-Salvador MB. Syringomyelia and Chiari malformation: A common etiology based on spinal cord tethering. Surg Neurol Int. 2011;2:139.
9. Ball MJ, Oldfield EH. Post-traumatic syringomyelia: Clinical features and surgical management. J Neurosurg Spine. 2003;99(2):199-205.
10. Alzate JC, Kothbauer KF, Jallo GI, Epstein FJ. Treatment of Chiari type I malformation in patients with and without syringomyelia: A consecutive series. Neurosurg Focus. 2001;11(1):1-8.