[Vaccine-associated paralytic poliomyelitis showing biphasic motor paresis].

We report a 38-year-old man with vaccine associated paralytic poliomyelitis (VAPP) which showed unusual biphasic worsening. The patient developed mild paresis of left upper and right lower extremities, five weeks after the oral poliovirus vaccination of patient's son and two weeks after the intramuscular injection of mumps/varicella vaccine in the left triceps muscle for himself. Needle electromyography (EMG) of his left arm and right leg was not remarkable, and the weakness recovered almost completely in three weeks. However, four weeks after the needle EMG, severe weakness and muscle atrophy of the four extremities, accentuated at the left arm and right leg, developed again. Cervical MRI showed gadolinium-enhanced, T(2) high-signal intensity area in the left C4-C6 anterior horn, most prominent at the height of C5 spine. Significant elevation of serum anti-poliomyelitis type 2 neutralizing antibody confirmed the diagnosis of VAPP. Immunomodulatory treatment, intravenous immunoglobulin (IVIg), did not improve weakness. We consider that the second clinical worsening of this patient was provoked by the needle EMG performed just after the first exacerbation, which injured the skeletal muscles and might have enhanced the retrograde transport of poliovirus via neural pathway.