Hereditary spastic paraplegia (HSP) is a clinically and genetically heterogeneous
group of disorders characterized by slowly progressive lower extremity spasticity
and weakness due to degeneration of the corticospinal tracts. Complicating symptoms
of HSP include cognitive impairment, seizures, amyotrophy and peripheral neuropathy.
Little is known about the natural history of HSP and tools to measure severity of
the disease are lacking. We aimed to develop and validate a HSP specific rating scale
for clinical assessment of functional impairment caused by HSP. The rating scale was
designed by a task force of the BMBF sponsored German Network of Hereditary Movement
Disorders.
The HSP rating scale focuses on key features of pure HSP; additional „complicating“
symptoms are recorded in an inventory. The scale is composed of three parts:
A. Functional score including maximum walking distance, gait quality and speed, capacity
to climb stairs and arise from a chair
B. Spasticity and weakness: evaluation following Ashworth scale and classification
of the British Medical Research Council
C. Additional symptoms of pure HSP including contractures, pain, sensory deficits
and bladder and bowel function
Every item is rated using a five point score. Maximum total score is 68 points.
In a first validation step 20 patients with HSP were investigated independently by
the study coordinator (RS) as well as the local HSP specialist.
Overall interrater variability determined by intraclass correlation coefficient (ICC)
was 0.84. ICC was >0.8 for all items of the functional score and was slightly less
(>0.7) for spasticity and weakness items. Substantial variability was observed for
rating of contractures (0.64) and sensory deficits (0.52).
Subscores and total score were correlated to landmarks of disability, a simple 4-point
severity scale evaluating walking capacities. Good prognostic values were calculated
for part A and C as well as the total score.
As an external plausibility test, we compared HSP ratings with the international co-operative
ataxia rating scale (ICARS) and the minimental status examination (MMSE). We found
good correlation between the HSP rating scale and ICARS (0.78) but poor correlation
with MMSE (-0.15), supporting plausibility of the HSP rating scale.
In a revised version of the HSP rating scale rater instructions for the assessment
of contractures have been modified and the item for sensory deficits has been removed.
Final validation is currently conducted.
