Intrathecal Baclofen: Spinal vs Cortical Spasticity — PMC 2010
Intrathecal baclofen was developed and first validated primarily in patients with spinal cord injury — whose spasticity originates in the spinal cord itself. PLS is different: it is a cortical-origin spasticity condition, meaning the disease process begins in the motor cortex and corticospinal tracts. This 2010 study directly compared ITB management between 57 patients with spinal versus cortical spasticity etiologies, asking whether origin of spasticity affects dosing requirements, delivery mode, clinical contacts, and outcomes. The answer, broadly: both groups respond similarly to ITB, but cortical spasticity patients need more adjunct therapy for upper extremity involvement.
What they did
Researchers at the University of Michigan Medical Center retrospectively reviewed charts of 57 consecutive patients seen in their outpatient spasticity clinic over three years, all of whom had received intrathecal baclofen pump implantation for severe spasticity. Patients were excluded if the cause of their spasticity was unknown.
The cohort included 7 patients with cerebral palsy, 8 with traumatic brain injury, 4 with stroke, 19 with multiple sclerosis, 10 with incomplete spinal cord injury, and 9 with complete spinal cord injury. Patients with MS were categorized within the spinal spasticity group based on the documented spinal cord lesion location — a categorization the authors acknowledge as imperfect, since MS patients may have both brain and spinal involvement.
The cortical spasticity group (CP, TBI, stroke) was compared to the spinal spasticity group (SCI, MS) on: daily baclofen dosage at 3, 6, 12, 24, and 36 months; number of clinic contacts and dose adjustments; delivery mode (simple continuous versus flex dosing); need for adjunct spasticity treatment after pump placement; and complication rates. Statistical analysis used linear mixed models for repeated measures data and Fisher exact tests for categorical comparisons.
What they found
The main finding is one of equivalence rather than difference. There were no statistically significant differences between the cortical and spinal spasticity groups in daily dosage (F = 0.121, P = 0.729), number of clinical contacts, or mode of delivery at any time point. Daily dosing increased significantly over time within both groups (F = 57.98, P ≤ 0.001), contrary to the common clinical assumption that ITB dosing stabilizes after an initial titration period.
The MS subgroup showed a statistically significant difference in daily dosing at the 6-month mark — mean 227 ± 203 mcg for MS versus 127 ± 67 mcg for the non-MS cohort (P = 0.020) — though this difference was not sustained at later time points.
The clearest difference between cortical and spinal groups was in the need for adjunct therapy to the upper extremities after pump placement. Thirty-three percent of all subjects needed adjunct spasticity treatment (botulinum toxin or phenol injections); of these, 74% had cortical spasticity and only 26% had spinal spasticity (P = 0.005). This reflects the anatomical reality that ITB, delivered into the intrathecal space, has less reach to the upper extremities — and cortical spasticity often involves significant upper limb involvement requiring focal treatment beyond what the pump can address.
The overall complication rate was 16% over three years, or 0.012 per month — slightly lower than the published literature average. Complications included 2 catheter migrations, 6 fractured catheters, and 1 pump infection with meningitis requiring catheter removal and replacement. Complication rates did not differ significantly between the cortical and spinal groups.
Why it matters
PLS involves cortical-origin spasticity — the upper motor neurons degenerate beginning in the motor cortex, not the spinal cord. When ITB was first developed and validated, the target population was people with spinal cord injuries. Understanding how well ITB translates to cortical-origin conditions like PLS requires exactly the kind of comparative data this study provides.
The key takeaway for PLS is twofold. First, cortical and spinal spasticity appear to parallel each other in terms of how ITB is managed — dosing, frequency of adjustments, and delivery mode are similar between groups. This supports using the broader ITB evidence base to inform decision-making in PLS, rather than requiring PLS-specific trials before proceeding.
Second, people with PLS who have significant hand or arm spasticity alongside their lower extremity symptoms may find that the ITB pump controls lower limb spasticity well but leaves upper limb spasticity less well addressed. The finding that 74% of adjunct therapy use after pump placement occurred in cortical spasticity patients is a practical signal: ITB plus focal botulinum toxin may be a better combination strategy than ITB alone for patients with significant upper extremity involvement.
Limitations and context
PLS patients were not enrolled in this study directly. The cortical spasticity group consisted of patients with cerebral palsy, traumatic brain injury, and stroke — all conditions involving cortical upper motor neuron dysfunction, but none identical to PLS pathophysiology. The extrapolation to PLS is scientifically reasonable but not proven.
The retrospective design, small sample sizes within subgroups, and attrition over three years all limit the strength of the conclusions. The authors are appropriately cautious: they describe their findings as hypothesis-generating rather than definitive, and they call for multicenter trials with larger samples to confirm the observations.
How this connects
This study sits at the intersection of two key questions for PLS patients: does ITB work for cortical-origin spasticity, and how does management differ from spinal spasticity? The answers — yes it works, and management is broadly similar with the exception of upper extremity adjunct needs — complement the PLS-specific findings in the ITB Utility in PLS short communication and the long-term efficacy data from the Spinal Cord 2004 study. Together, these three studies form the core evidence base for ITB in PLS. The practical implications are summarized on the Spasticity management page.
Citation
Chiodo AE. Intrathecal baclofen for spasticity management: a comparative analysis of spasticity of spinal vs cortical origin. Journal of Spinal Cord Medicine. 2010 Feb;33(1):16–21. doi:10.1080/10790268.2010.11689670. PMC2853324.