Sex: M
Vaccine: FLUX, FLUX
Symptoms: Pain in extremity, Pyrexia, Radial nerve palsy
Clinical narrative: Case number PHHY2014US062688 is an initial literature report received on 21 May 2014. The author discussed about a case of radial nerve motor palsy following seasonal influenza vaccination. This report refers to a 26 years old male patient. He was right hand dominant surgical resident. His concomitant medication was not reported. He was vaccinated with seasonal influenza vaccine (unknown manufacturer, batch number: not reported) intramuscularly in the lateral brachium just distal to the deltoid on specified date. After 12 to 16 hours after vaccination he experienced wrist drop and inability to extend his left thumb or digits. He denied having radicular pain or paresthesias during inoculation. He experienced localized pain that involved the upper arm and shoulder lasting 2 to 3 days. Motor palsy began as clumsiness while typing on a keyboard and progressed to a complete wrist drop with lack of digital extension over 3 to 4 hours. He denied having history of traumatic injury to the left upper extremity, recent febrile illness, night sweats, chills, or any dermatologic rash. His review of systems was negative with the exception of the described motor deficits. He had received extensive workup and clinical examination by several specialists. After 6 weeks of injury he underwent sensory and motor nerve conduction studies on left median, radial and ulnar nerves as well as the right radial nerve. Results were consistent with an isolated motor palsy of the radial nerve. Needle electromyogram demonstrated complete denervation of all radial nerve innervated muscles distal to the triceps with positive sharp waves and no voluntary motor unit potentials. All other motor groups tested were normal. He had physical examination at 6 weeks after injury recorded severe (0/5) weakness in the left radial nerve-innervated muscles with the exception of the triceps. His physical examination was otherwise normal, with preserved sensation to light touch and two point discrimination throughout the left upper extremity. He again had physical examination after 5 months after injury; he had improvement in motor wrist extension but no active thumb extension or digital extension of the metacarpophalangeal joints. Sensation remained intact throughout the left upper extremity. Tinel sign was negative at the brachial plexus, radial tunnel, pronator, and dorsal radial sensory nerve. Reflexes were 2/2 throughout, and cervical spine screening was negative. The brachioradialis demonstrated 4/5 muscle strength. He was managed with physical therapy and splinting. He gradually recovered motor function over the next 3 months in a pattern characteristic of proximal to distal re-innervation. The first muscle to regain function was the brachioradialis and the last muscle was the thumb extensors and extensor indicis proprius. After follow up of 8 months post injury he had recovered 5/5 strength in the wrist extensors and 4/5 strength in the finger extensors. After follow up of 14 months post injury he had both current and retrospective QuickDASH survey. Where his scored improved from 64 at the time of the initial palsy to 14 (scores reported on a 0 to 100 scale with higher score reflecting greater disability). The work and sports/performing arts modules of the QuickDASH were also done and showed improvement from 56 to 19 and 56 to 31 respectively. It was reported that he had difficulty with power grip when playing golf or racquet sports as the most currently limiting sequelae of the palsy. The outcome of the events was reported as complete recovery. The seriousness of the events was not reported. The author concluded that intramuscular injection carries a small but serious risk of nerve injury, which may be unknown or unappreciated by medical practitioners. When these cases presented to the specialist efforts should be made to distinguish PTS (Parsonage Turner Syndrome) and direct nerve injury. The clinical spectrum of these conditions may overlap, making definitive diagnosis difficult. In this case, precise causation of the palsy as either PTS or direct nerve injury was unclear because common features of both are seen. Additionally post injection neuropalsy does not automatically imply negligent injection technique; all clinicians should be reminded of the potential for direct injury to the radial nerve by improper injection technique.