Spastic Myopathy in Adults With Cerebral Palsy

Maximal ambulation speed over 10 meters, barefoot

Passive ankle dorsiflexion were assessed using standardized Tardieu Scale procedures. XV1 was measured during a very slow, strong passive stretch of the gastrocnemius with the patient supine, knee extended. The stretch was performed over 3-5 seconds to minimize stretch-reflex activation, and the maximal angle at which soft-tissue resistance could no longer be overcome was recorded as the passive maximal dorsiflexion range (XV1).

XV3 was obtained under identical positioning as XV1 but during a rapid stretch (V3). To ensure the muscle was fully relaxed prior to the fast movement, the examiner performed several quick oscillatory pre-movements in the opposite direction. The angle of catch or clonus during the fast stretch defined XV3.

XA represented maximal active dorsiflexion, measured with the patient supine and knee extended, reflecting both passive and active constraints imposed by the gastrocnemius.

Participants were assessed using a share wave elastography system while seated in an isokinetic ergometer (trunk at 60°, knee extended, ankle fixed). The lateral gastrocnemius (GL) shear modulus (µGL) were measured through nine sites (superior, middle, inferior, medial, medium, lateral). Measurements were performed under two ankle positions: 40° plantarflexion (non-stretched LG) and 80% of individual XV1-GAS (stretched LG). For each site and condition, 10-second cine loops were recorded (a validated acquisition method), yielding 10 videos per participant. Each video was then divided into 10 DICOM frames to obtain reliable µGL estimates. Image processing and µGL extraction were performed using MATLAB®.

Participants were assessed using a high frequency ultrasound system while seated in an isokinetic ergometer (trunk at 60°, knee extended, ankle fixed). Structural ultrasound images at the middle/medium location were analyzed to derive fascicle length

Participants were assessed using a hifh frequency ultrasound system while seated in an isokinetic ergometer (trunk at 60°, knee extended, ankle fixed). Structural ultrasound images at the middle/medium location were analyzed to determine muscle thickness

A high-field 3T MRI examination of both the paretic and contralateral lateral gastrocnemius muscles will be performed using a flexible surface coil positioned around the patient's calves. Muscle volume will be quantified from a series of continuous axial T1-weighted slices acquired along the full length of the calf.

A high-field 3T MRI examination of both the paretic and contralateral lateral gastrocnemius muscles will be performed using a flexible surface coil positioned around the patient's calves. Intramuscular fat percentage will be estimated using a Dixon sequence, allowing reliable separation of water and fat signals.

A micro-invasive muscle biopsy using a Weil-Blakesley forceps will be performed twice, one year apart, on both the paretic and contralateral lateral gastrocnemius of each participant. This technique will be carried out by a trained investigator under local anesthesia. The biopsy will target the LG muscle belly, yielding approximately 30 mg of tissue for in vitro biomechanical analysis. Using an MTS Insight machine, fresh muscle fragments will undergo sequential uniaxial tensile and compressive relaxation tests. These procedures will enable detailed quantification of hyperelastic behavior under compression.

From biopsies, ~30 mg of tissue will be cryosectioned to visualize 400-500 fibers. Immunohistochemistry will determine fiber-type composition (fast/slow myosin)

From biopsies, ~30 mg of LG tissue will be cryosectioned to visualize 400-500 fibers. Standard stainings (H&E, Gomori Trichrome, COX, Sirius Red) will assess endo-/perimysial fibrosis.

From biopsies, ~30 mg of LG tissue will be used to examine the expression of 57 genes related to skeletal muscle structure, myogenic differentiation, metabolic regulation, and atrophy pathways. RNA will be extracted with the Nano PreAMP kit (Qiagen), and gene expression profiled using the RT² Profiler™ PCR Array - Human Skeletal Muscle Development & Disease. The targeted gene groups include markers of the dystrophin-glycoprotein and titin complexes, fast and slow fiber signatures, energy metabolism, myogenesis (MYOD1, MYOG, PAX3/7), atrophy/autophagy (FBXO32, TRIM63, TNF)

Participants will be equipped with bilateral surface EMG electrodes on the tibialis anterior and lateral gastrocnemius (ME6000, 16-channel WiFi system; 1000 Hz). LG spastic cocontraction will be quantified during maximal dorsiflexion effort. When technically feasible, Mmax will be used as an alternative denominator of MVC in these ratios through tibial nerve stimulation

Participants will be positioned in the ConTrex device, at two ankle positions (40° plantarflexion = relaxed GL; and 80% XV1-GAS = stretched GL). The maximal strength in dorsiflexion and plantarflexion will be quantified by the isokinetic ergometer.