Clinical Case Analysis

Transcribed Clinical Notes

• Patient: 15-year-old male, resident of Kalyan
• Presenting complaint: 2 months history of weakness in bilateral lower limbs
• Onset: Insidious, gradually progressive
• After a few days (due to this): difficulty maintaining balance while walking
• Went to a nearby hospital; doctor gave medicine (DNA - did not attend/no response/DNE noted), no improvement
• Went to another hospital for investigation on 3/7/26

1. Nerve Conduction Study (NCS): Evidence of sensorimotor demyelinating with secondary axonal polyneuropathy affecting bilateral upper and lower limbs
2. MRI Dorso-lumbar Spine: Subtle T2 hyperintense signal intensity in the posterior aspect of thoracic cord T5 to T11, without contrast enhancement or cord expansion - findings suggest myelopathy

Clinical Analysis

Dual Pathology: Combined Myelopathy + Polyneuropathy

• Peripheral: Sensorimotor demyelinating polyneuropathy with secondary axonal involvement (NCS proven, bilateral upper and lower limbs)
• Central: T2 hyperintensity in posterior thoracic cord T5-T11 without enhancement or cord expansion (MRI-proven myelopathy)

Priority Differential Diagnoses

1. Subacute Combined Degeneration (SCD) - Vitamin B12 Deficiency (TOP PRIORITY)

• Posterior column T2 hyperintensity on MRI (T5-T11, no enhancement, no expansion) - exactly matching the "inverted V" or posterior column signal described in SCD
• Combined myelopathy + peripheral demyelinating polyneuropathy - SCD causes both simultaneously
• Gradually progressive course over 2 months
• Adolescent with possible nutritional deficiency (vegetarian diet common in this region)
• NCS showing demyelinating polyneuropathy is consistent - B12 deficiency demyelinates both central and peripheral myelin

2. CIDP (Chronic Inflammatory Demyelinating Polyneuropathy) + Concurrent CNS Demyelination

• CIDP explains the NCS findings perfectly (sensorimotor demyelinating, bilateral, with secondary axonal change)
• However, CIDP typically does NOT involve the spinal cord on MRI; CNS involvement would suggest an overlap syndrome (e.g., CIDP + MS or NMO)
• Less likely in a 15-year-old as a primary explanation for both findings

3. Neuromyelitis Optica Spectrum Disorder (NMOSD) + Peripheral Neuropathy

• NMOSD can cause longitudinally extensive transverse myelitis, but typically with cord expansion and enhancement
• T5-T11 is a long segment - NMO-IgG (anti-AQP4 antibody) should be tested
• Peripheral demyelinating NCS findings are unusual for NMOSD

4. Copper Deficiency Myelopathy

• Produces identical MRI picture to SCD (posterior column T2 signal)
• Can also cause peripheral neuropathy
• Less common but must be considered, especially if B12 is normal

5. Infectious / Parainfectious (HTLV-1, HIV, Lyme)

• HIV-associated myelopathy + neuropathy is a classic combination
• HTLV-1 myelopathy (tropical spastic paraparesis) - endemic in some parts of India
• Check serology

6. Hereditary/Genetic (Adrenomyeloneuropathy, Friedreich Ataxia)

• Both can cause myelopathy + neuropathy in young patients
• Usually more slowly progressive; genetic testing warranted if metabolic causes excluded

Recommended Next Workup

Key Diagnostic Clues from MRI Description

• Subacute combined degeneration (B12 / copper deficiency) - posterior > lateral columns, long segment, no enhancement
• Distinguishes from inflammatory myelitis (which typically shows enhancement in acute phase and cord swelling)
• Distinguishes from MS plaques (which are typically smaller, patchy, asymmetric)

Most Likely Working Diagnosis