Can a syrinx (fluid-filled cavity) cause arm and leg pain and numbness?

Can a Syrinx Cause Arm and Leg Pain and Numbness?

Yes, a syrinx can definitively cause both arm and leg pain and numbness, depending on its location and extent within the spinal cord. The specific symptoms depend on which spinal cord levels are affected by the fluid-filled cavity.

Symptom Patterns Based on Syrinx Location

Cervical Syrinx (Neck Region)

• Upper extremity symptoms predominate when the syrinx involves the cervical spinal cord 1, 2
• Patients typically present with numbness and weakness in the hands, burning dysesthesias (abnormal sensations) in the forearms, and decreased strength in finger movements 1
• Sensation may be decreased to light touch in all fingers of both hands 1
• Radicular pain in the arms is a common presenting symptom 2, 3

Thoracic Syrinx (Mid-Back Region)

• When isolated to the thoracic region, lower extremity symptoms are more typical 2
• However, if the syrinx extends rostrally (upward) from a thoracic origin into the cervical region, both upper and lower extremity symptoms can occur simultaneously 2

Extensive Syrinx Involvement

• A syrinx can span multiple spinal levels—documented cases show extension from C1 (first cervical vertebra) down to T7 (seventh thoracic vertebra) or beyond 2, 4
• When both cervical and thoracic cord are involved, patients present with symptoms in both arms and legs 2
• The clinical presentation evolves as the syrinx expands, with progressive worsening of symptoms over time 2

Key Clinical Features to Recognize

Sensory Symptoms

• Paresthesias (tingling, pins-and-needles sensations) in affected limbs 3
• Numbness affecting specific dermatomes corresponding to the syrinx level 1, 3
• Burning dysesthesias, particularly in the forearms when cervical cord is involved 1

Motor Symptoms

• Progressive weakness in affected muscle groups 1, 2
• Graded weakness (e.g., 4/5,3/5, or worse strength) in specific muscle groups like biceps, triceps, wrist extensors, and finger muscles 1
• Difficulty controlling the legs and wobbly gait when lower cord is affected 1

Pain Patterns

• Radicular pain (shooting pain along nerve distributions) in arms or legs 2, 3
• Mechanical spinal pain at the level of the syrinx 3
• Pain characteristics help distinguish syrinx from other causes 1

Underlying Causes to Investigate

The most important clinical principle is that a syrinx is rarely an isolated finding—you must identify the underlying cause 1, 4:

Chiari Malformation (Most Common)

• Chiari Type I malformation is the most common cause, accounting for 43% of syrinx cases 1, 4
• Syringes associated with Chiari are characteristically wide (>5 mm) and have their cranial extent in the cervical spine 4
• The combination of width >5 mm and cervical location has 99% specificity for Chiari-associated syrinx 4

Spinal Cord Compression

• Cervical spondylosis (degenerative spine disease) can cause syrinx formation through intermittent cord compression 5
• Arachnoid webs in the thoracic spine can obstruct CSF flow and lead to syrinx development 2
• Congenital spinal canal narrowing predisposes to syrinx formation 1

Other Causes

• Spinal dysraphism (7.4% of cases), tumors (5.5%), and tethered cord (4.8%) 4
• Post-traumatic syrinx can develop after spinal cord injury 1
• Approximately 30% of syringes are idiopathic (no identifiable cause) 4

Critical Diagnostic Approach

Imaging Requirements

• MRI of the complete spine is mandatory for evaluating suspected syrinx 1
• Both T1- and T2-weighted sequences are required to demonstrate the syrinx and any associated cord edema 1
• Assess for Chiari malformation on brain/cervical MRI, as this is the most common association 1, 4
• Evaluate for spinal cord compression from disc herniation, spondylosis, or arachnoid webs 1, 2, 5

Size and Location Matter

• Document syrinx width, length, and cranial/caudal extent 4
• Syringes >5 mm wide with cervical involvement strongly suggest Chiari malformation 4
• Small slitlike cavities (<5 mm) may represent persistent central canal rather than true syringomyelia and are often asymptomatic 3

Important Clinical Caveats

Not All Syringes Are Symptomatic

• Slitlike syrinx cavities (1-5 mm diameter) are often incidental findings and may represent remnants of the central canal 3
• In one series, 16 of 32 patients with small syringes had alternative diagnoses explaining their symptoms 3
• These small cavities typically do not change in size over time and may not require treatment 3

Progressive Nature

• Syringomyelia is a progressive disease that can expand rostrally with concomitant worsening of symptoms 2
• Patients may experience postoperative worsening of symptoms initially, even after appropriate decompression 1
• Regular follow-up with repeat MRI is necessary to monitor for expansion 2

Distinguish from Pseudoclaudication

• Leg pain and numbness from syrinx must be distinguished from vascular claudication, spinal stenosis, and peripheral arterial disease 1
• Vascular claudication is exercise-induced and relieved with rest, whereas syrinx symptoms are typically constant or positional 1
• Check for diminished pulses and vascular risk factors to exclude arterial causes 1

Treatment Implications

When Surgery Is Indicated

• Surgical intervention is warranted for progressive neurological symptoms, documented syrinx expansion, or functionally disabling symptoms 2
• Treatment addresses the underlying cause (e.g., Chiari decompression, arachnoid web excision, cervical decompression for spondylosis) 2, 5
• Surgical resection can be curative with possible remission of symptoms and normalization of spinal anatomy 2

Conservative Management

• Small, stable, asymptomatic syringes may be observed with serial MRI 3
• Physical therapy and pain management may help with symptoms while monitoring 6
• Do not assume the syrinx is causing symptoms—look for alternative explanations first 7, 3