Effect of Intrathecal Baclofen on Bladder Function in Patients With Severe Supraspinal Spasticity

Neurogenic bladder dysfunction is a prevalent condition characterized by impaired bladder control resulting from neurological conditions, for example, spinal cord injury or traumatic brain injury (TBI). Detrusor overactivity is a typical symptom of central nervous system damage. A lesion affecting the pontine neural network typically results in loss of tonic inhibition exerted by the pontine micturition center and causes involuntary detrusor contractions. Intrathecal baclofen (ITB), primarily indicated for spasticity management, holds potential in addressing the underlying mechanisms of neurogenic bladder dysfunction.

Urodynamic data were extracted from clinical charts of patients with severe supraspinal spasticity who received ITB treatment. Urodynamic studies were performed before pump implantation (PRE), after surgery (POST), and when achieving an effective steady state ITB dosage (ss-ITB), as reflected by a reduction in Modified Ashworth Scale (MAS) score. To determine potential risk factors for a poor response to ITB with respect to bladder function, patients were post hoc categorized into good and poor responders based on post void residual volume at ss-ITB.

Apart from significantly reducing MAS scores, ITB caused significant increases in reflex volume, bladder capacity, and residual volume, and significant decreases in maximal detrusor and vesical pressures. Significant differences between good and poor responders (with respect to bladder function) were noted for reflex volume, bladder capacity, and residual volume at ss-ITB, whereas no urodynamic parameter served to differentiate the two groups at PRE.

This study confirms a beneficial effect of ITB on bladder function in patients with severe supraspinal spasticity. However, concurring with the literature, a small subgroup of patients experienced serious deterioration in terms of increased reflex volume and residual volume, posing the risk of subsequent renal damage. Unfortunately, no urodynamic parameter predicted such a poor response to ITB before treatment initiation.