LAUSR

Abstract Rationale: Herpes zoster frequently causes dermatomal vesicular rash accompanied by severe neuralgia, and reaching a differential diagnosis may be challenging before the appearance of the vesicular rash. Patient concerns: A 40-year-old male patient visited the emergency department with a complaint of sudden onset motor weakness and ipsilateral radiating neuralgia to the Lt. thigh. He had suffered from chickenpox during childhood. Diagnoses: No skin lesion was present at the initial visit. The reverse Straight Leg Raise test was negative. Magnetic resonance imaging showed asymmetrically swollen dorsal root ganglion with Gadolinium enhancement. The vesicular rash that appeared on the sixth day after the symptom onset led to the diagnosis of herpes zoster. Interventions: Antiviral agent of valacyclovir (1000 mg t.i.d.) was administered for 7 days. Outcomes: The patient recovered from motor weaknesses by 2 weeks from the onset of the symptom. Mild degree post-herpetic neuralgia recovered by 2 months. Lessons: A high index of suspicion is necessary to differentiate early herpes zoster radiculitis before the appearance of vesicular rash from compressive radiculopathy. In L2–3 ipsilateral radiating pain along the dermatome or myotome, the absence of reverse Straight Leg Raise sign may be a possible factor in differentiating herpes zoster radiculitis from compressive radiculopathy.