Botulinum Toxin Injections as an Intervention for Spastic Diplegia in a Case of Mucolipidosis Type IV: A Case Report

Case Diagnosis: Mucolipidosis Type IV

Case Description or Program Description: A 2-year-old female with a medical history of global developmental delay and general hypotonia presented to PM&R clinic for heel cord tightness with dorsiflexion up to 10 degrees bilaterally. Initial treatment included physical, occupational, and speech therapy with early intervention and AFO braces. A genetics workup diagnosed Mucolipidosis Type IV (MLIV), a rare neurodegenerative lysosomal storage disorder whereby most affected infants exhibit hypotonia, intellectual disability, developmental milestone delays, and/or psychomotor retardation. Despite therapy and bracing, by age 7, she developed spastic diplegic gait with toe walking, and her ankle contractures worsened to -30 degrees dorsiflexion in the left and -10 degrees in the right, necessitating a wheelchair for mobility.

Setting: Tertiary Care Hospital; Bronx, NY

Assessment/Results: At age 7, the patient received botulinum toxin injections in both lower legs. Post-injection, left ankle dorsiflexion improved to -5 degrees and the right to neutral, and she regained assisted ambulation. By age 9, she received 6 total injection treatments with fluctuating function. Her most recent assessment showed dorsiflexion to neutral bilaterally. Her mother reported improved assisted ambulation with and without AFOs, highlighting functional gains.

Discussion (relevance): A neurodegenerative component of MLIV has become widely appreciated, with majority of individuals demonstrating progressive spastic quadriparesis and loss of psychomotor skills in the second decade of life. This case introduces botulinum toxin as a potential intervention for spasticity in MLIV, a disease with no approved cure or corrective management. While the efficacy of botulinum toxin for treating spasticity is well-accepted, little is documented regarding spasticity second to MLIV. The patient showed the greatest improvements following the first injection, followed by a plateau, suggesting botulinum toxin may also serve as a maintenance therapy.

Conclusions: As part of a multi-modal intervention plan incorporating therapy and assistive devices, botulinum toxin injections may be beneficial adjunct treatment for spasticity secondary to MLIV.