Acquired brain injury (ABI) produces impairment simultaneously across cognitive, communicative, motor, sensory, neurobehavioural, somatic, and participation domains, yet clinicians typically characterise this breadth by combining several separate instruments. This narrative review asks a focused question: how well do existing validated instruments capture the full profile of impairment after ABI in a way that is feasible for routine specialist-clinic use and longitudinal tracking, and what is required to close any remaining gap? Drawing on the International Classification of Functioning, Disability and Health (ICF) and consensus outcome frameworks, the review appraises global outcome measures, comprehensive brain-injury instruments, and domain-specific tools against contemporary measurement standards. Validated instruments exist for most individual domains and for global outcome, and at least one comprehensive measure profiles multiple domains with strong psychometric support. However, no single, concise, ICF-aligned instrument has been established for routine multidomain impairment profiling and serial tracking across the full range of ABI aetiologies in the specialist clinic. The review argues that this feasibility-and-integration gaprather than any absence of validated components-is the principal unmet need, and it outlines a staged programme to develop and validate an integrated ABI impairment profile as a future direction. The review is conceptual; any new instrument requires full psychometric validation before clinical use.