In an 18-year-old athlete with a three-year history of pain and loss of pain and temperature sensation in the right T6‑T8 trunk dermatomes without skin changes, what diagnoses should be considered?

Dissociated Sensory Loss in T6-T8 Dermatomes: Consider Syringomyelia or Intramedullary Pathology

This 18-year-old athlete presenting with isolated loss of pain and temperature sensation (while preserving other sensory modalities) in a dermatomal distribution strongly suggests an intramedullary spinal cord lesion, most likely syringomyelia, and requires urgent MRI of the thoracic spine without contrast.

Key Diagnostic Reasoning

The clinical presentation reveals a critical pattern:

• Dissociated sensory loss (pain/temperature affected, but presumably touch/proprioception preserved) indicates damage to the spinothalamic tract within the spinal cord itself
• The unilateral dermatomal distribution at T6-T8 suggests a focal intramedullary process
• The 3-year chronicity without skin changes rules out peripheral nerve or dermatologic causes
• The absence of motor deficits (not mentioned) suggests early or localized cord pathology

Primary Differential Diagnoses to Consider

1. Syringomyelia (Most Likely)

• Classic presentation of dissociated sensory loss in a "cape-like" or segmental distribution
• Occurs when fluid-filled cavity (syrinx) expands within the spinal cord, first damaging crossing spinothalamic fibers
• Can be associated with Chiari malformation, trauma, or idiopathic causes
• Young age fits typical presentation

2. Intramedullary Spinal Cord Tumor

• Ependymoma or astrocytoma can present with slowly progressive sensory changes
• The 3-year timeline is consistent with slow-growing lesions
• Pain is common with these lesions

3. Spinal Cord Arteriovenous Malformation (AVM)

• Can cause progressive myelopathy with sensory changes
• Less common but important not to miss

4. Demyelinating Disease (Less Likely)

• Multiple sclerosis or transverse myelitis typically has more acute onset
• Usually involves multiple modalities and bilateral symptoms

Immediate Diagnostic Approach

MRI thoracic spine without IV contrast is the essential first imaging study 1. According to ACR guidelines, when myelopathy or radiculopathy is present, MRI of the thoracic spine is the initial imaging modality of choice for identifying actionable pathology 1.

Specific MRI Protocol Considerations:

• Without contrast is sufficient initially 1 - will identify syrinx, cord expansion, or mass lesions
• Sagittal T2-weighted sequences are particularly sensitive for detecting syrinx (appears as hyperintense fluid signal within cord)
• If tumor suspected after initial MRI, contrast can be added subsequently

Clinical Examination Pearls:

• Test for dissociation: specifically check if light touch and proprioception are preserved while pain/temperature are lost
• Assess for motor weakness in lower extremities (suggests cord compression)
• Check for hyperreflexia or Babinski sign (indicates upper motor neuron involvement)
• Examine for scoliosis (associated with syringomyelia)
• Palpate for thoracic spine tenderness (suggests structural pathology)

Important Clinical Pitfalls

Do not assume this is radiculopathy: While thoracic radiculopathy can cause dermatomal pain 1, isolated dissociated sensory loss without motor findings is atypical for nerve root compression. Additionally, radicular pain patterns are often non-dermatomal (64.1% in lumbar spine, 69.7% in cervical spine) 2, making the precise dermatomal pattern here more suspicious for cord pathology.

Do not delay imaging: The presence of neurologic deficits (sensory loss) constitutes a "red flag" requiring immediate investigation 1. This is not simple thoracic back pain without neurologic findings.

Do not attribute to sports injury alone: While trunk injuries are common in athletes 3, isolated dissociated sensory loss is not explained by musculoskeletal or peripheral nerve injuries typical in sports.

Why This Matters for Morbidity and Mortality

Untreated syringomyelia or intramedullary tumors can lead to:

• Progressive irreversible spinal cord damage
• Development of motor weakness and paralysis
• Bladder/bowel dysfunction
• Chronic neuropathic pain

Early diagnosis allows for:

• Surgical intervention if indicated (syrinx drainage, tumor resection, Chiari decompression)
• Prevention of permanent neurologic disability
• Better functional outcomes and return to sport

The 3-year duration without progression is somewhat reassuring but does not eliminate the need for urgent evaluation - some syrinxes and tumors progress slowly but can suddenly worsen.