Dr Mariappan is a widely recognised authority in:

Neurological Rehabilitation, including stroke, traumatic brain injury (TBI), spinal cord injury, and progressive neurodegenerative conditions.
Amputee Rehabilitation, including prosthetic and non-prosthetic pathways.
Spasticity Management, including advanced use of botulinum toxin with ultrasound guidance and intrathecal baclofen.
Musculoskeletal Rehabilitation using integrated biopsychosocial approaches.
Health Systems Leadership, quality improvement, and education in rehabilitation care.

He has served as Principal Investigator in numerous national and international clinical trials, including PhEAST, STIM-MS, and EASE, and has contributed to over a dozen peer-reviewed publications and book chapters on stroke, spasticity, amputee rehabilitation, and service evaluation.

In his medico-legal capacity, Dr Mariappan acts as an Expert Witness for both Claimant and Defendant cases (60:40 split), with formal training through the NRC Expert Witness Course (2024) and completion of the Bond Solon Certificate (2025).

Areas include:

Traumatic Brain Injury
Spinal Cord Injury
Complex Neurological Disability
Functional Neurological Disorder
Musculoskeletal Injury
Complex Polytrauma
Amputation
Pain Management
Spasticity Interventions (ultrasound)