A 32-year-old man from rural Maharashtra presents with rapidly progressive ascending paralysis and areflexia over 5 days following an upper respiratory infection. CSF analysis shows protein 120 mg/dL with normal cell count. Which single feature best distinguishes Guillain-Barré Syndrome from acute transverse myelitis in this clinical context?

## Distinguishing GBS from Acute Transverse Myelitis (ATM) ### Key Discriminating Feature **Key Point:** The presence of a **sensory level** is the hallmark finding that distinguishes acute transverse myelitis from GBS. A sensory level indicates a spinal cord lesion and is virtually pathognomonic for ATM. ### Comparative Table | Feature | Guillain-Barré Syndrome | Acute Transverse Myelitis | |---------|-------------------------|---------------------------| | **Sensory level** | Absent (no spinal cord lesion) | **Present** (defines the condition) | | **Reflexes** | Areflexia (early and consistent) | Initially brisk, then may diminish | | **Progression** | Ascending, distal-to-proximal | Rapid onset, then plateau | | **CSF findings** | Protein ↑, cells normal/low | Pleocytosis (often >50 WBC/μL) | | **MRI spine** | Normal | T2 hyperintensity spanning ≥3 vertebral segments | | **Motor pattern** | Distal > proximal initially | Symmetric, affects all limbs at same level | ### Why This Matters Clinically **Clinical Pearl:** A sensory level—loss of sensation below a specific spinal dermatome—indicates a focal spinal cord lesion. GBS is a **peripheral neuropathy** affecting nerve roots and peripheral nerves, NOT the spinal cord, so sensory loss is non-anatomic (stocking-glove) and there is no sensory level. **High-Yield:** In GBS, areflexia is early and universal; in ATM, reflexes may initially be brisk (upper motor neuron pattern) because the lesion is at the cord level. ### Mnemonic **LEVEL = Lesion Evident (myelitis); GBS = Global (no level)** --- ## Why Each Distractor Is Misleading - **Areflexia with preserved motor power initially:** Both conditions can present with areflexia early. This is NOT discriminating. - **CSF protein elevation with normal/low cell count:** While typical of GBS, ATM can also show elevated protein (though pleocytosis is more common in ATM). This overlaps. - **Rapid progression over days:** Both GBS and ATM progress rapidly. This feature is shared, not discriminating.