A 2.5-year-old boy has no words, no pointing, does not respond to name, has repetitive hand-flapping, and prefers spinning objects. He had 5-6 words at 18 months that he subsequently lost. The MOST important initial investigation to guide management is:

• A EEG to rule out Landau-Kleffner syndrome
• B Hearing assessment (BERA/ABR) and metabolic screen ✓
• C Chromosomal microarray (CMA) and fragile X testing
• D MRI brain with diffusion-weighted imaging

Explanation

Any child with language regression and suspected autism spectrum disorder (ASD) must first have hearing assessed as a mandatory first-line investigation — hearing loss is a common, treatable cause of language delay that can mimic ASD. BERA (ABR) is objective and does not require cooperation. Metabolic screening (thyroid, amino acids, organic acids) identifies treatable conditions. Chromosomal microarray and fragile X testing are important second-line genetic investigations for ASD but the immediate priority is ruling out a sensory deficit. EEG is warranted if Landau-Kleffner (epileptic aphasia) is suspected with nocturnal seizures, but the regression here follows a different pattern. MRI is not first-line for ASD evaluation.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.