Botulinum Toxin A Adult Gastrocnemius Muscle Study

The study aims to compare the effectiveness of BOTOX-A® (botulinun toxin A) placed between two different injection sites, namely at the proximal portion of the gastrocnemius(GCM) versus at the midbelly of the GCM.

Previous studies have used the midbelly of a muscle as the position where the motor endplates are most densely located. The reasoning behind this method was based on the previous works that showed most bands of cholinesterase activity to be located in specific topographical patterns at the center of the muscle fiber. These results have been used as landmarks to place the injections. Current standard guidelines recommend that botulinum toxin be placed at the 4 quadrants of the midbelly portion of the gastrocnemius (GCM) muscle. However, recent cadaveric research studies on the distribution of the intramuscular endings of the GCM suggest that the highest branch density is found within the upper 20-30% length of the calf. Therefore, in accordance to the theory that effect of botulinum toxin are greatest at sites where the intramuscular endings are most dense, the location where these toxins should be placed would be at these proximal sites of the GCM rather than at the midbelly.

40 recruited patients will be allocated into either the intramuscular ending targeted (ie.upper portion of calf) or midbelly targeted group.

Each subject will undergo a total number of 4 assessments; prior to the injection and 2,4and 8 weeks post injection.

Eligibility Criteria:
Inclusion Criteria:

* Male or female, 20 \< age \< 70 year old
* Hemiplegia documented after ischemic or hemorrhagic stroke, documented by CT (computed tomography) or MRI (magnetic resonance imaging) scan
* Time between the onset of stroke \< 24 months
* Individuals who have been medically stable for at least 4 weeks prior to study enrollment
* Confirmed equinovarus with spastic hypertonia of the ankle
* Spasticity as defined by a MAS greater than grade 1 +
* Botulinum toxin -naive patients
* Participants who can complete the 10 meter walking test with caregiver or walking tool assistance within 8 and 45 seconds, on 2 occasions
* Participants who will have stable treatment regimen and concomitant medication during the trial period

Exclusion Criteria:

* The patient has any of the following medical conditions that is contraindication to botulinum toxin exposure; pregnancy, lactation, neuromuscular disease, aminoglycoside, antibiotic concurrent to botulinum toxin treatment
* Fixed contracture of the ankle, previous history of surgical procedure performed on the ankle
* Cognitive deficit that disables patients to give informed consent to the procedure
* Concomitant progression of any CNS (central nervous system) or PNS (peripheral nervous system), or myopathy, or uncontrolled seizure. Underlying CNS insult should be controlled and in stable condition with no further risk of progression and further deterioration of patient's current neurological status. Those with multiple sclerosis or multiple systemic atrophy are to be excluded
* Significant cutaneous or joint inflammation
* URI or other systemic infection that would mandate the use of antibiotic concurrent to botulinum toxin injection
* Anticoagulation treatment with INR (International Normalized Ratio) greater than 3.0
* Upper extremity spasticity greater than MAS grade 4 that may limit gait function
* Subjects with previous episodes of motor point block injection using phenol or other chemodenervating agents
* Subjects with intrathecal baclofen pump