Chronic Exertional Compartment Syndrome (CECS) Treated With Abobotulinumtoxin A

Chronic exertional compartment syndrome (CECS) is an underdiagnosed condition and a cause of lower extremity pain often observed in running athletes. In runners, CECS is characterized by a reversible increase in pressure within an inelastic fascial compartment(s) of the lower extremity, leading to compromised tissue perfusion and subsequent pain and neurologic symptoms. It impacts both pediatric and adult populations. As currently diagnosed and treated, chronic exertional compartment syndrome presents unique challenges. Evaluation of CECS includes a thorough history and physical exam to rule out other causes of exertional leg pain, but the differential diagnosis must remain high on the list. Needle manometry, an invasive and painful procedure, is therefore used to confirm the diagnosis of CECS by measuring intra-compartmental pressure (ICP).

A growing literature, however, positions ultrasound shear wave elastography (SWE) as a viable and attractive alternative to ICP testing as it is both non-invasive and cost-effective. Earlier efforts demonstrated that muscle compartment "hardness" may accurately and noninvasively predict ICP. Building on these, SWE now provides direct measures of related mechanical properties of muscle and compartment, namely, "stiffness", thereby demonstrating promise as a diagnostic tool for CECS. Fasciotomy, currently the most well-accepted treatment approach, still has a significant number of treatment failures, demonstrating the need for additional options. A series of case reports have highlighted the potential merits of botulinum toxin as an alternative non-invasive treatment to surgery. Further, there is a growing consensus that desired BoNT targeting is best achieved through incorporating ultrasound guidance during the injection. The largest case series study to date reported that 15/16 patients with CECS had complete exertional pain relief with aboBoNTA. However, the apparent high dosing also led to a reduction in strength in 11/16 patients - An average of 288 units for the anterior compartment and 180 for the lateral compartment. In sum, the optimal dosage has yet to be determined.

Recently, the research team reported a case of a 39-year-old female runner presenting with lower extremity pain. CECS was confirmed with ICP. In addition, SWE was utilized in diagnosis and management. Briefly, SWE testing showed post-exercise increases in "stiffness" in the right Tibialis Anterior and left Fibularis Brevis relative to baseline measures. To provide perspective, both pre- and post-exercise SWE measures were elevated in this patient compared to two age and sex-matched controls. Following onaBoNTA treatment, further SWE measures revealed a reduction in patient muscle stiffness from the initial pre- and post-exercise treadmill testing, reaching levels comparable to the two asymptomatic age and sex-matched controls by week 6. Collectively, these results support a relationship between changes in intra-compartmental pressure as measured by needle manometry and muscle compartment "stiffness" as measured by SWE, and, as such, a role for SWE in CECS diagnosis and management.

In sum, SWE-based diagnosis coupled with ultrasound-enhanced injection accuracy are introduced to potentially complement and/or replace traditional approaches, which have challenged the diagnosis and management of CECS.