A 44-year-old man was carried to the hospital in an ambulance because of dyspnea, paralysis and dysuria after signs of the flu. Acute encephalomyelitis was diagnosed by examination of magnetic resonance imaging. Antimicrobial treatment and respirator management was carried out with indwelling of urethral catheter for urinary retention. After improvement of encephalitis, the urethral catheter was removed. However, he still needed medical care because of persistent lower urinary tract symptoms. He complained of urge incontinence and urination frequency. Decrease of functional bladder capacity was noticed in a frequency volume chart. After consulting with our neurologist, acute transverse myelitis was diagnosed from imaging and neurological findings. Pressure flow study (PFS)demonstrated detrusor overactive during the filling phase and insufficient contractility during the voiding phase. We reached the diagnosis of detrusor hyperactivity with impaired contractility (DHIC). We did not introduce clean intermittent catheterization but used the mirabegron instead. Although storage symptoms did not improve on the mirabegron monotherapy, the symptoms improved by solifenacin added. There is a possibility that combination therapy with mirabegron and solifenacin is effective for DHIC.