Photo-stimulation with low reactive level laser is reported to have some specific neurobiological effects such as inhibition of Aδ- and C- fibre nerve conductions, activation of central descending inhibitory system, and suppression of local synaptic neurotransmission. It is widely used to relieve pain in our clinical site. 
Micturition reflex, in particular storage reflex, is constructed by spinal reflex via peripheral Aδ-fibre afferent nerves, and it is controlled by central descending inhibitory system. In patients with neurological diseases, neurogenic overactive bladder is common and it is due to neurogenic detrusor hyperactivity. Detrusor hyperactivity is mainly due to abnormal micturition reflex is due to abnormal spinal reflex via peripheral Aδ- and C- fibre afferent nerves and abnormal signals of those afferent nerves.  
Then photo-stimulation will be applicable to modulate and normalize abnormal micturition reflex without deterioration of bladder contraction, resulting in ameliorating storage dysfunction without influence of voiding dysfunction. We previously reported that the photo-stimulating with low reactive level laser can improve lower urinary tract dysfunction (LUTD) in some neurological disease models such as spinal cord injury and Parkinson disease (PD). 
In this study, we evaluate photo-stimulating effect on overactive bladder (OAB) in patients with neurological diseases preliminary.

Six patients are recruited (Progressive supranuclear palsy (PSP) n=1, PD n=1, Cervical spondylosis n=1, Neurosarcoidosis n=1). Questionnaire of OAB, and urodynamic study (cystometry and pressure flow study) were performed before and just after single stimulation, and after twelve stimulations (twice per week). Storage function (maximum bladder capacity (BC), bladder capacity at first involuntary contraction (FIC)) and voiding function (flow rate, detrusor pressure at maximum flow rate, residual urine) were investigated. Photo-stimulation with low reactive level laser was irradiated to bilateral S2, S3 and S4 intervertebral foramens via two probes contacted to the body.

After single stimulation, storage function was slightly improved (bladder volume at first desire to void +10.9 (14.1) (average (SD))%, maximum bladder capacity +4.3 (16.7) %, bladder capacity at first involuntary contraction +11.2 (11.0) %). On the other hand, voiding function (flow rate, detrusor pressure at maximum flow rate, residual urine) was unchanged. After twelve stimulations (twice per week), OAB symptom was ameliorated and storage dysfunction was improved more (bladder volume at first desire to void +16.7 (36.7) %, maximum bladder capacity +6.88 (37.6) %, bladder capacity at first involuntary contraction +18.7 (38.6) %). Voiding function (flow rate, detrusor pressure at maximum flow rate, residual urine) was unchanged. Two patients of them also received additional twelve stimulations, because they had felt not effective or slight effective. In the both cases, storage dysfunction was improved more after twenty four stimulations. Patient had not complained during and after the stimulation.

Photo-stimulation using low reactive level laser to S2, S3 and S4 intervertebral foramens improved OAB symptoms and storage dysfunction without exacerbation of voiding dysfunction in patients with neurological diseases. Percutaneous photo-stimulation with low reactive level laser to around bilateral S2-4 root may modulate lower urinary tract function and ameliorate not voiding dysfunction but storage dysfunction. It may be due to improvement of abnormal spinal reflex via peripheral Aδ- and C- fibre afferent nerves and abnormal signals of those afferent nerves.

Photo-stimulation using low reactive level laser to S2, S3 and S4 intervertebral foramens may improve OAB symptom and storage dysfunction without exacerbation of voiding dysfunction. Although further investigation should be needed, It may be a new and useful device for neurological OAB.