6 6Journal ofNeurology, Neurosurgery, anid Psychiatry 1996;60:6-13 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.1.6 on 1 January 1996. Downloaded from NEUROLOGICAL INVESTIGATIONS Investigation of the neurogenic bladder Clare J Fowler Methods of examination which have been analogue signals but with the advances in used to investigate the neurogenic bladder electronics and development of microchip include tests of bladder function, so-called technology the machines have become pro- "urodynamics", and neurophysiological tests gressively more complex, more "intelligent", of sphincter and pelvic floor innervation. A and mostly easier to use. Today measured possible consequence of a neurogenic bladder is pressures are digitised allowing on line, real damage to the upper urinary tract but the time computer analysis of signals. investigation of such complications is essen- During the development of urodynamics an tially urological and is only briefly mentioned important advance came with the introduction in this review. of facilities to record pressure measurements superimposed on the fluoroscopic appearances of the bladder, a "videocystometrogram". History of the development of This combination provides a complete picture investigations of the behaviour of the bladder both during URODYNAMICS filling and emptying although it is expensive The term "urodynamics" encompasses any and exposes the patient to x rays. Much can be investigation of urinary tract function although learnt from simple cystometry alone and it is it is often used colloquially as a synonym for this investigation which is now a standard cystometry. Cystometry, the measurement of facility in almost every district general hospital bladder pressure, has been the main tool used with a urology department. to show abnormal behaviour of the neurogenic The hydrodynamic problems of measuring bladder. fluid flow are different from measuring pres- The earliest reference to a study measuring sure within an organ. Introduction of simple bladder pressure is commonly given as the and cheap equipment for measuring urinary http://jnnp.bmj.com/ paper by Mosso and Pellacani published in flow rate' has led to this becoming routine; 1882.1 With a water manometer they showed combined with ultrasound measurement of that bladder pressure rose at the start of mic- the postmicturition residual volume, it pro- turition and then gradually declined but that vides a simple non-invasive means by which during storage the pressure measured within much valuable information can be obtained the organ gave little indication of what volume about lower urinary tract function. it contained. However, the paper which described a technique for cystometry produc- NEUROPHYSIOLOGICAL INVESTIGATIONS on September 26, 2021 by guest. Protected copyright. ing what is regarded as the precursor of modem Various types of neurophysiological investiga- day urodynamic recordings was published in tion of the pelvic floor and the sphincters have Brain in 1933 by Denny-Brown and been developed over the years. A neurophysio- Robertson2 from the National Hospital for logical method for recording the bulbocaver- Nervous Diseases, Queen Square. By means nosus reflex, regarded as clinically valuable in of an ingenious system of mirror manometers assessing patients with neurogenic bladder dis- they recorded intravesical and intraurethral orders, was first reported in 1967." pressure with two transurethral catheters (one Neurophysiological recordings of various inside the other), as well as recording rectal, pelvic floor reflexes were much in vogue in the perineal, and abdominal wall pressures in 1970s but have since lapsed and have been three neurologically normal men. From their transiently replaced by an enthusiasm for findings they defined the physiological recording the pudendal evoked potential. sequence of processes which occur with blad- Recording from the striated muscle of the der filling, the initiation of micturition, and urethral sphincter or anal sphincter during voiding to completion. cystometry was first recommended as a means The introduction of cystometry into clinical of detecting inappropriate sphincter contrac- disorder The National Hospital practice was gradual and by the 1960s it was tion during detrusor contraction, the for Neurology and being used in only a few specialised urological known as detrusor sphincter dyssynergia.7 For Neurosurgery, centres.3 When commercial equipment first several reasons this type of kinesiological Queen Square, London now little used sphincter WC1N 3BG, UK became available it consisted of a series of pen EMG is although C J Fowler recorders which recorded pressure changes as EMG performed as a separate neurophysio- Investigation of the neurogenic bladder 7 Figure 1 Filling J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.1.6 on 1 January 1996. Downloaded from cystometry in a healthy subject. Vinfus = infusion at 50 mllminute; Pabd = intrabdominal . .. : . pressure measured by the . .. I I I . : . = . .. .. : . .. rectal line; Pves . I . intravesical . ... pressure; . = . .. I . Pdet Pves-Pabd. .. ... : Respiratory movements, I III I I I . II . I I I which were not recorded . .. I . I : . .. .. h. with the intravesical --A-P%&amLm&A- Pves J _......................... ....................... .................... pressure measurements, 10 cm H20 were recorded with the rectal pressure line so that these appear as an artefact ~~~~~~~~~~~~~~~~~~~~~.... Pdet due to subtraction on Pdet. 10 cm H20 In the early part ofthe trace the subject was asked to @. .@.. ;@@... .. .... cough and the subtraction Pabd .. ofPabdfrom Pves was 1.... .. .. -.. 10 cm H20 complete so that no rise in Pdet is recorded. Vinfus ........................................... .................. .@*........................- 1:13 3:13 5:13 7:13 9:13 100 ml Cough Time (min:s) logical test remains a valuable investigation in ical and intrabdominal pressures a fine some circumstances. catheter is passed through the urethra into the bladder and another into the rectum. The catheter used to monitor intravesical pressure Principle underlying investigations is passed, together with a somewhat wider CYSTOMETRY diameter catheter through which the bladder is Cystometry is the recording of the pressure- filled. Important information is obtained if volume relation of the bladder. The intravesi- detrusor pressure is measured both during fill- cal pressure is measured and by subtracting ing and while the patient attempts to mic- the intra-abdominal pressure from this figure turate. In the interests of saving time an an estimate of the true pressure produced by unphysiologically rapid rate of filling of 50 the smooth muscle of the detrusor is obtained. ml/min is commonly used in cystometric This is best seen by looking at the preparatory studies. stages of cystometric recordings when the Recently, methods have become available patient is asked to cough (fig 1). Coughing for recording bladder pressures over periods of raises the intra-abdominal pressure and thus many hours and the bladder is left to fill natu- the measured intravesical pressure but under rally, so-called "ambulatory urodynamics".8 physiological conditions the detrusor does not In patients with neurogenic incontinence http://jnnp.bmj.com/ then contract so that the derived detrusor the commonest finding is of an abrupt rise in pressure (Pdet) remains unchanged or detrusor pressure which the patient is unable becomes slightly negative because the intra- to suppress and which is usually accompanied abdominal pressure may rise more than the by reports of urinary urgency (fig 2). If the intravesical pressure. To measure the intraves- patient is recognised as having a neurological Figure 2 Detrusor hyperreflexia in a woman on September 26, 2021 by guest. Protected copyright. with multiple sclerosis. to 100 ml . .. .. .. ... .. .. Afterfilling . : . (vinfus) there was a Q r detrusor contraction which . .. .. ... .. ... ..... .. .5 m Is . .. .. ... ............ .. .. ... * .. ... resulted in a pressure rise of A ... 90 cm H20. Vinfus ............. ,i. 100 ml Pves ~~~~~~~~~~~~~~~. .... ... 10 cm H20 .. ...... .....--*-.....t*t* ---- -*v* @@*- Pdet :1*\...''.''''..'........ 10 cm H20 @o@@@@v**-**-*vv*s~~~~~~~~~~~. .. Padb 10 cm H20 1:02 2:02 3:02 4:02 5:02 ~~~~~~~~~~~~~~...... Time (min:s) 8 Fowler J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.60.1.6 on 1 January 1996. Downloaded from Figure 3 Abrams 100 - This has resulted in a large body of medical nomogram. Using values literature in which patients are classified for the maximalflow a 80 - (Qmax) and the I Obstructed according to their urodynamic findings rather corresponding voiding E 60 - than by the underlying pathophysiological a -0 detrusor pressure (Pdet) 40 - cause and diagnosis. point can be plotted on the Equivocal In patients with suspected obstruction of nomogram that determines CL 20 - Unobstructed whether the bladder outlet is / 1 outflow, particularly men with prostatic hyper- obstructed, unobstructed, or 0- trophy, measurement of detrusor pressure equivocally obstructed. ) 5 10 15 20 Qmax (ml/s) during voiding is important. This, together with urinary flow rate provides information about the outflow tract" and an estimate of condition, this is called "detrusor hyper- the presence of obstruction can be made reflexia", the condition is otherwise referred to (fig 3). as "detrusor instability"9-the cystometric changes in the two conditions being indistin-