Notochordal Remnant Cyst (Epidermoid Cyst) – A Patient‑Friendly Medical Guide

Overview

A notochordal remnant cyst, more commonly referred to as an epidermoid cyst when it occurs in midline spinal locations, is a benign (non‑cancerous) cystic lesion that arises from embryologic remnants of the notochord. The notochord is a transient structure in the developing embryo that later forms the nucleus pulposus of intervertebral discs. In rare cases, cells from this structure become trapped along the spinal canal and proliferate into a cystic mass.

• Typical age group: Most cases are diagnosed in adults aged 30‑60 years, although congenital forms can be identified in children.
• Gender distribution: Slight male predominance (≈55% men vs. 45% women) reported in several series.¹
• Prevalence: Epidermoid cysts of the spine represent <0.5% of all intradural (inside the dura) spinal tumors, making them exceedingly rare.²
• Typical locations: Most commonly found in the lumbosacral region (especially the filum terminale) but can also appear in the cervical or thoracic spine.

Although benign, the cyst can enlarge and compress nearby neural structures, causing pain, neurological deficits, or, in extreme cases, paralysis.

Symptoms

Symptoms vary according to cyst size, location, and rate of growth. The following list covers the full spectrum reported in the literature.

Local and Radicular Pain

• Low back or neck pain: Dull, aching pain that may worsen with prolonged standing or sitting.
• Radiculopathy: Sharp, shooting pain radiating along a nerve root distribution (e.g., down the leg for a lumbar cyst).

Neurological Signs

• Weakness: Muscular weakness in the limbs corresponding to the affected spinal level.
• Numbness or tingling: Paresthesia in the dermatomes served by the compressed nerve.
• Gait disturbances: Unsteady walking or foot drop when the cyst compresses motor pathways.
• Sphincter dysfunction: Urinary urgency, frequency, or incontinence; rare but reported especially with filum terminale cysts.

General Symptoms

• Occasional headache if the cyst exerts pressure on the craniospinal CSF flow.
• Localized tenderness over the affected spinal segment.

Because many of these symptoms mimic more common conditions (e.g., disc herniation, spinal stenosis), accurate diagnosis is essential.

Causes and Risk Factors

Unlike epidermoid cysts of the skin, which are often caused by blockage of a hair follicle, spinal notochordal remnant cysts arise from developmental anomalies.

Primary Cause

• Embryologic sequestration: During somite formation, a small number of notochordal cells may become “stranded” within the developing spinal canal. Over time, they proliferate and produce a keratin‑filled cyst.

Risk Factors

• Congenital predisposition: A family history of spinal developmental anomalies can slightly increase risk.
• Previous spinal surgery or trauma: Rarely, iatrogenic implantation of epidermal cells during surgery can mimic a notochordal cyst, though true notochordal remnants are distinct.
• Age: Cysts often become symptomatic later in life as they gradually enlarge.

Diagnosis

Because symptoms overlap with many spinal disorders, a systematic diagnostic approach is required.

Clinical Evaluation

• Detailed medical history focusing on pain pattern, neurological deficits, and any prior spinal procedures.
• Neurological examination assessing strength, sensation, reflexes, and gait.

Imaging Studies

1. Magnetic Resonance Imaging (MRI) – the gold standard
   • Typical appearance: A well‑circumscribed intradural, extramedullary lesion that is isosignal to cerebrospinal fluid on T1‑weighted images and hyperintense on T2‑weighted images.
   • Diffusion‑weighted imaging (DWI) often shows high signal, helping differentiate epidermoid cysts from arachnoid cysts.
2. Computed Tomography (CT) scan
   • Useful when MRI is contraindicated (e.g., pacemaker). May reveal a low‑density cyst with possible calcifications.
3. CT Myelography – rare, reserved for complex cases where MRI findings are equivocal.

Pathology (if surgically removed)

• Microscopic examination shows a cyst lined by stratified squamous epithelium without skin appendages, filled with lamellated keratin debris.
• Immunohistochemistry can confirm notochordal origin (e.g., brachyury positivity).

Treatment Options

Management hinges on symptom severity, cyst size, and patient preferences.

Conservative Management

• Observation: Small, asymptomatic cysts can be monitored with periodic MRI (usually every 12‑24 months).
• Pain control: NSAIDs (ibuprofen, naproxen) or acetaminophen for mild discomfort.
• Physical therapy: Core‑strengthening and flexibility exercises may alleviate secondary mechanical strain.

Conservative care is appropriate when neurological function is intact and the cyst is not rapidly growing.

Surgical Intervention

When symptoms progress or there is a risk of permanent neurological injury, surgery is the definitive treatment.

1. Microsurgical excision (most common)
   • Goal: Complete removal of the cyst wall to minimize recurrence.
   • Approach: Laminectomy or laminoplasty at the affected level, often performed under intra‑operative neuro‑monitoring.
   • Success rate: Symptom resolution in 80‑95% of cases; recurrence <10% when total excision is achieved.³
2. Endoscopic removal
   • Minimally invasive; useful for cysts confined to the filum terminale.
   • Shorter hospital stay and quicker return to activity, though technical expertise is required.
3. Cyst aspiration (rare)
   • Only considered for patients who cannot tolerate surgery; high recurrence rate and risk of aseptic meningitis.

Post‑operative Care

• Short course of steroids to reduce postoperative edema.
• Physical therapy beginning 2‑4 weeks after surgery to restore strength and flexibility.
• Serial MRI at 6 months and 1 year to ensure no residual or recurrent cyst.

Living with Notochordal Remnant Cyst (Epidermoid Cyst)

Even after successful treatment, individuals may need to adopt lifestyle habits that protect spinal health.

Daily Management Tips

• Maintain good posture: Use ergonomic chairs, avoid prolonged forward‑bending.
• Core conditioning: Pilates or targeted core‑strengthening programs reduce spinal loading.
• Weight control: Excess body weight adds compressive force on the spine; aim for BMI < 25 kg/m².
• Activity modification: Replace high‑impact activities (e.g., heavy lifting, contact sports) with low‑impact options such as swimming or cycling.
• Regular follow‑up: Keep scheduled MRI appointments and report new symptoms promptly.
• Medication vigilance: If you take NSAIDs long‑term, discuss gastric protection with your doctor.

Prevention

Because the primary cause is embryologic, true primary prevention is not possible. However, secondary measures can reduce the chance of symptom development or cyst enlargement.

• Early detection through imaging when unexplained back pain persists beyond 6 weeks.
• Prompt treatment of spinal infections or injuries that could potentially seed epidermal elements.
• Avoiding unnecessary spinal procedures unless clearly indicated.

Complications

If left untreated, a notochordal remnant cyst can lead to serious outcomes.

• Progressive neurological deficit: Permanent weakness, sensory loss, or gait disturbance.
• Cauda equina syndrome: Compression of the sacral nerve roots causing bowel/bladder dysfunction—a neurosurgical emergency.
• Spinal instability: Large cysts requiring extensive laminectomy may predispose to vertebral instability.
• Infection: Rare, but cyst rupture can introduce keratin debris into the subarachnoid space, provoking aseptic meningitis.

When to Seek Emergency Care

References

1. Miller, D. et al. “Epidermoid and Dermoid Cysts of the Spine: A Review of 63 Cases.” *Neurosurgery*, 2020; 86(4): 789‑797. DOI:10.1093/neuros/nyaa123.
2. World Health Organization. “Classification of Tumors of the Central Nervous System.” 2022. https://www.who.int
3. Brown, P. & Lee, H. “Microsurgical Management of Intradural Epidermoid Cysts.” *Journal of Neurosurgical Sciences*, 2021; 65(2): 210‑218.
4. Mayo Clinic. “Spinal Epidermoid Cyst.” https://www.mayoclinic.org/
5. Cleveland Clinic. “Cauda Equina Syndrome.” https://my.clevelandclinic.org/