Urodynamic investigations in patients with multiple system atrophy (MSA) commonly show detrusor overactivity (DO) as the underlying cause of decreased bladder volumes at first sensation, reduced bladder capacity and urgency incontinence. Incomplete bladder emptying is a significant feature of MSA and worsens with the progression of illness. The bladder neck, also known as the internal urethral sphincter, is an important component in the maintenance of continence and receives sympathetic innervation from the hypogastric nerve. Careful analysis of bladder abnormalities can be helpful in distinguishing between MSA-P and Parkinson's disease (PD), although DO causing urgency and frequency occurs in both conditions, patients with MSA are more likely to have a high PVR, detrusorsphincter dyssynergia and an open bladder neck at the start of bladder filling on videocystometrogram and a neurogenic electromyography (EMG) of the anal sphincter.