Bilateral brachial plexus neuritis in a dog. What Is Your Neurologic Diagnosis?

A 10-year-old 11.7kg neutered male Patterdale Terrier was referred to the University of Edinburgh with an acute onset progressive five day history of lethargy, pyrexia, hyporexia,cervical and left thoracic limb hyperesthesia, stiff thoracic limb gait and low head carriage. Two ticks had been removed from the dog three days prior to onset of clinical signs. The referring veterinarian treated the dog with enrofloxacin for three days prior to referral (5 mg/kg every 24
ours) and dexamethasone once two days prior to referral (0.2mg/kg). Initially the patient seemed more comfortable but on the day of referral, he had marked hyperesthesia on cervical and left thoracic limb manipulation and was reluctant to ambulate preferring to remain in lateral recumbency. Radiographs of the cervical region were unremarkable.