Generalized weakness after focal injection of botulin toxin type A (BTA)

Objective: Botulinum toxin type A (BTA) is established treatment for muscle, autonomic nerve terminal overactivity.BTA is primarily presynaptic neuromuscular blocking agent inducing selective. reversible muscle weakness lasting several months when injected intramuscu1arly.The toxin in therapeutic doses is safe.Generalizcd weakness of distant muscles is seldom reported. BTA is digested ingastrointestinal tract as it forms complex with proteins that protect and stabilize ncurotoximit considered treatment option for gastrointestinal achalasia. Methods: A75 year old diabetic woman developed functional obstructive gastrointestinal symptoms due to esophageal achalasia. She received endoscopically epicardial BTA injection (Botox Aller- gan I00 U).By day 3 patient developed shortness of breath, dysarthria, dysphagia, nasal regurgitation.By day 7 she exhibited respiratory distress.When admitted to ICU (day 8) patient was alert; eye movements were full with normally reactive pupils. There was neck flexor, upper, lower limb weakness graded Z/5-3/5 respectively (MRC scale).Deep jerks were brisk throughout. Results: Blood tests showed anemia; tumor marker titer, autoim- mune screenings, antibody scarch of muscle tyrosin kinase, acetilcholine receptors, voltage gated calcium channels were negative.Brain,total body computed tomography was inconclusive. Three Hz repetitive nerve stimulation(RS)on day 8 showed 25 % decrement of ulnar compound muscle action potential(CMAP). Repeated low rate RS(day I2) revealed up tol8% CMAP decrement before and after activation.No increment was recorded at 20 Hz whereas initial CMAPs were low in amplitude(l—2 mV). Overall findings suggested severe neuromuscular transmission defect. Necdle electromyography (day I2, 45) showed widespread denervation. increased brief duration polyphasia. Oral pyridostigmine bromide(60 mg every 4 hour)was commenced on day 8. Four courses of plasma exchanges (PEX) were given from day 21.By day 48.patient was able to protrude her tongue,to bend upper, lower limbs. By day 5, she developed respiratory failure due to superimposed pneumonia from which she recovered. Conclusions: Our patient exhibited neuromuscular junction (nmj) disorder chronologically related to BTA injection.Electi-ophysiology suggested transmitter release block.The disorder partially responded to oral anticholincsterases and PEX. In our view,pathogencsis was related either to distant effect of BTA or to uncover underlying nmjdisorder.