Journal ofNeurology, Neurosurgery, and Psychiatry 1997;62:473-477

Assessment of autonomic dysreflexia in patientswith spinal cord injury

Armin Curt, Boris Nitsche, Biljana Rodic, Brigitte Schurch, Volker Dietz

Swiss ParaplegicCentre, UniversityHospital Balgrist,Zurich, SwitzerlandA CurtB NitscheB RodicB SchurchV DietzCorrespondence to:Dr Armin Curt, UniversityHospital Balgrist,Forchstrasse 340, CH-8008Zurich, Switzerland.Received 10 April 1996Accepted 3 December 1996

AbstractObjectives and methods-To assess theimpairment of supraspinal control overspinal sympathetic centres and the occur-rence of autonomic dysreflexia in patientswith spinal cord injury. Autonomic dysre-flexia is caused by the disconnection ofspinal sympathetic centres from supra-spinal control and is characterised byparoxysmal hypertensive episodes causedby non-specific stimuli below the level ofthe lesion. Therefore, patients with spinalcord injury were examined clinically andby different techniques to assess theoccurrence of autonomic dysreflexia andto relate disturbances of the sympatheticnervous system to episodes of autonomicdysreflexia.Results-None of the paraplegic patients,but 59% (13/22) of tetraplegic patients(91% of the complete, 27% of the incom-plete patients) presented signs of auto-nomic dysreflexia during urodynamicexamination. Only 62% of the tetraplegicpatients complained about symptoms ofautonomic dysreflexia. Pathological sym-pathetic skin responses (SSRs) of thehands were related to signs of autonomicdysreflexia in 93% of cases. No patientwith preserved SSR potentials of thehands and feet showed signs of autonomicdysreflexia, either clinically or duringurodynamic examination. Ambulatoryblood pressure measurements (ABPMs)indicated a loss of circadian blood pres-sure rhythm (sympathetic control) butpreserved heart rate rhythm (parasympa-thetic regulation) only in patients withcomplete tetraplegia. Pathological ABPMrecordings were seen in 70% of patientswith symptoms ofautonomic dysreflexia.Conclusions-The urodynamic examina-tion was more sensitive in indicating signsof autonomic dysreflexia in patients withspinal cord injury, whereas SSR allowedthe assessment of the degree of discon-nection of the sympathetic spinal centresfrom supraspinal control. Using ABPMrecordings the occurrence of episodes ofautonomic dysreflexia over 24 hours andthe effectiveness of therapeutical treat-ment can be assessed.

(7 Neurol Neurosurg Psychiatry 1997;62:473-477)

Keywords: spinal cord injury; autonomic dysreflexia;urodynamic examination; 24 hour ambulant bloodpressure measurement; sympathetic skin response

In patients with spinal cord injury both thespinal somatic (motor-sensory) and autonomic(sympathetic) nervous system can be affected.1Therefore, patients can have sympathetic fail-ure (for example, orthostatis) due to a discon-nection of the spinal sympathetic centres fromsupraspinal control (hypothalamus, brain-stem).2 ' By contrast with the spinal sympa-thetic pathway, parasympathetic nerve fibresinnervating the cardiovascular system are con-veyed by the vagus nerve and run outside thespinal cord.4 Therefore, patients with spinalcord injury usually have autonomic failure dueto the disconnection of the spinal sympatheticsystem whereas cardiac parasympathic path-ways remain unaffected.) 6

Autonomic failure can lead to autonomicdysreflexia characterised by paroxysmal hyper-tensive episodes combined with headache,profuse sweating, and concurrent bradycar-dia.7-9 Due to the loss of supraspinal sympa-thetic control, non-specific stimuli below thelevel of injury (for example, bladder disten-sion, rectal manipulation, painful stimuli tothe skin) can induce excessive sympatheticspinal outflow below the level of lesion, whichcauses the cardiovascular changes.'0 11 Thissympathetic hyperactivity is balanced by acti-vation of the vagus nerve via the baroreceptorreflex, which leads to the concurrent bradycar-dia.12 13 An adequate diagnosis and manage-ment of autonomic dysreflexia is critical forthe rehabilitation programme of patients withspinal cord injury, as these episodes are poten-tially fatal. 14 Those patients with a level ofinjury higher than T6 are particularly prone toautonomic dysreflexia. Therefore, this studyfocused on improving the diagnostic assess-ment of the spinal sympathetic nervous systemand autonomic dysreflexia in patients withtraumatic tetraplegia.The aim of this study was to evaluate the

effect of impaired function of the descendingsympathetic spinal tract on (1) the sympa-thetic skin responses (SSRs); (2) the results of24 hour ambulant blood pressure measure-ments (ABPMs); and (3) the frequency ofoccurrence of symptoms of autonomic dysre-flexia during urodynamic examination. Thesevariables would be expected to provide infor-mation related to the damage of the spinal

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sympathetic tract in patients with spinal cordinjury and also to indicate the best diagnosticapproach for the assessment of autonomic dys-reflexia even if it is not clinically evident.

Patients and methodsPatients with chronic (> 6 months post-trauma) paraplegia and tetraplegia due to trau-matic spinal cord injury who were admitted tothe paraplegic centre between 1993 and 1995were studied. All patients were younger than65 and none were receiving cardiac or hyper-tensive treatment. Furthermore, patients wereexcluded if they had a history of cardiovasculardiseases (coronary heart disease, arrhythmias,hypertension, or orthostatic dysregulation).All patients underwent neurological examina-tion according to the international AmericanSpinal Injury Association (ASIA) protocol,allowing the classification of the lesion aseither complete or incomplete (any sensory ormotor function in the sacral dermatomes). 1

Furthermore, the ASIA motor (maximum 100points) and sensory scores (maximum for bothaesthesia and algesia 112 points) indicated theseverity of the spinal cord lesion.

SYMPATHETIC SKIN RESPONSEFor the evaluation of the function of thedescending spinal sympathetic tract the SSRof the right hand and foot were examined inaccordance with techniques described else-where.'6 20 The SSR was recorded using con-ventional EMG apparatus (Amplaid). SurfaceEMG disc electrodes (gold cup, Dantec) wereattached to the ventral and dorsal surface ofthe right hand and foot. The SSR wasrecorded over 10 seconds and sampled at aband pass of 0-3 Hz to 3 kHz. Electrical stimu-lation was applied using single, square pulses(0-2 ms duration, 10-20 mA) to the contralat-eral median nerve at the wrist. To avoidpathological SSR recordings due to lesions ofthe afferent nerve fibres (for example, in trau-matic tetraplegic patients) a second methodwas performed in parallel. Single, transcorticalmagnetic stimuli were applied (Mag Pro,Dantec, Denmark) using a flat round coil(MC 125 Coil Dantec, 1-4 Tesla) localisedover Cz (according to the international 10-20system). The stimulus duration was 0-1 msand the intensity 80-100 A/ps. To preventhabituation the interstimulus interval was setat 60 seconds for both stimulation techniques.In accordance with other studies the SSRpotentials were considered to be normal whenthey could reliably be reproduced three timesby both stimulation techniques. Those poten-tials which were either not sufficiently repro-ducible or absent were classified aspathological.

TWENTY FOUR HOUR AMBULATORY BLOOD

PRESSURE MEASUREMENTThe ABPM was performed with a SpaceLabs90207 Ambulatory Blood Pressure System(SpaceLabs Medical GmbH, Kaarst) as previ-ously described.21 23 Systolic blood pressure,diastolic blood pressure, and heart rate were

measured and recorded automatically. For sta-tistical analysis, measurements recorded every20 minutes between 0800 and 1200 repre-sented the day period, whereas hourly record-ings from midnight to 0400 represented thenight period. This definition was made for thefollowing reasons. During defined day periodspatients were involved in an intensive rehabili-tation programme, usually mobilised in awheelchair. The period of bed rest (nightperiod) usually started at midnight and ended,depending on the state of rehabilitation, at0400 with the next bladder emptying.Therefore, the definition of the day/nightperiod was adapted to the particular needs ofthe patients in the rehabilitation programme.

URODYNAMIC EXAMINATIONPatients were examined urodynamically whilein a supine position with 15° pelvic obliquity.Two microtransducer catheters (No 5 and 3radio-opaque, 8F) were used for the ure-throvesical and anorectal pressure recordingsrespectively.24 Proper location of the transduc-ers was controlled by image intensifier. Slowbladder filling (5 ml/min) was performed with a24% contrast medium (3-acetylamino-methyl-5-acetylamino-2,4,6-tribenzoic acid). Drugsthat could interfere with the urethrovesicalfunction were discontinued 24 hours beforeexamination. In all patients blood pressureand heart rate were continuously monitoredthroughout the examination (Ohmeda 2300Finapress). As described elsewhere,25 thepatients were expected to exhibit signs of auto-nomic dysreflexia, when they showed paroxys-mal systolic and diastolic hypertensiveepisodes with concurrent bradycardia due tomanipulations of the bladder (bladder disten-sion, voiding, catheter positioning).

DATA ANALYSISThe mean (SD) of the ABPM, systolic bloodpressure, diastolic blood pressure, and heartrate examinations were calculated and the sig-nificance of any differences were determinedwith a two tailed, paired t test. The level of sig-nificance was set at P < 0-01.

ResultsPATIENTSParallel studies were performed on 22 patientswith chronic tetraplegia (11 complete, 11incomplete; 18 men, four women) and ninepatients with complete paraplegia (level oflesion < T6, seven men, two women). Thesecond group served as controls, as they werenot likely to develop autonomic dysreflexia.Table 1 shows the demographic and clinicaldata (ASIA scores).

SYMPATHETIC SKIN RESPONSENo patient with complete tetraplegia displayednormal SSR potentials in the hands or feetusing either of the stimulation techniques. Inall patients with complete paraplegia SSRpotentials of the hands could be recorded, butonly 60% (six of 11) gave responses of the feet.In 73% (eight of 11) of the patients with

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Assessment ofautonomic dysreflexia in patients with spinal cord injury

Table 1 Demographic and clinical data of the tetraplegic and paraplegic patients studied

ASIA scores (mean SD)Level of Age

Patients injury mean (range) motor (max 100) algesia (max 112) aesthesia (max 112)

Complete tetraplegia C4-C7 29-3 17 20 24(n = 11) (17-56) (9 2) (4-6) (15)

Incomplete tetraplegia C2-C8 40-1 80 91 91(n= 11) (15-64) (24) (25) (23)

Complete paraplegia T6-L4 33-4 52 65 68(n=9) (19-50) (3 9) (17) (18)

incomplete tetraplegia (as defined by the ASIAprotocol which focuses on somatic nerve func-tion) normal SSR potentials could be recordedin both the hands and the feet (fig 1).Therefore, the clinical ASIA classificationfailed to accurately assess the extent of discon-nection of the spinal sympathetic system in27% (three of 11) of patients within the groupwith incomplete spinal cord injury.No patient with preserved SSR potentials of

the hands and feet showed symptoms of auto-nomic dysreflexia either clinically or duringurodynamic examination. Conversely, allpatients with symptoms of autonomic dysre-flexia showed pathological SSR potentials ofthe hands and feet. Loss of SSR potentials ofthe hands was associated with symptoms ofautonomic dysreflexia in 93% (12 of 13) of thepatients.

TWENTY FOUR HOUR AMBULATORY BLOODPRESSURE MEASUREMENTAll patients with incomplete tetraplegia (n =20 recordings) and the patients with completeparaplegia (n = 10 recordings) showed nor-mal circadian rhythmicity of blood pressure(fig 2A). The mean systolic blood pressureduring the day period was 118-2 (13-2) mmHg with a significant reduction during thenight period to 109-1 (8 4) mmHg (P <0'001). The same was true for the diastolic

Figure 1 (A) Normalsympathetic skin responseof the hands (upper traces)andfeet (lower traces) ofahealthy subject (H). (B)Loss of the response in apatient with completetetraplegia (P).

E0

0

0.a)ccn

_A

- H

Jl l1

_B

- p

Time (s)

blood pressure with reduction from 72-5(9-7) mmHg to 62-9 (6-5) mmHg (P <

0*0001). In 91% (10 of 11) of patients withcomplete tetraplegia (n = 32 recordings) thephysiological rhythmicity of circadian bloodpressure was absent (fig 2B, C). There was nosignificant difference between the values of theday period (systolic blood pressure 109-7(8 5) mm Hg; diastolic blood pressure 62-6(7-5) mm Hg) and those of the night period(systolic blood pressure 113-6 (9A4) mm Hg;diastolic blood pressure 63X1 (8- 1) mm Hg).Two patients with complete tetraplegia with

symptoms of autonomic dysreflexia andepisodes of severe cardiovascular dysregula-tion (paroxysmal hypertensive episodes up to224 mm Hg with concurrent bradycardia upto 46 bpm) disclosed a pathological ABPMprofile reflecting these episodes (fig 2B). Aftereffective treatment (antihypertensive drugs,sphincterotomy) the ABPM profile showedthe characteristics of patients with completetetraplegia (loss of circadian rhythmicity)without the episodes of severe blood pressuredysregulation (fig 2C).By contrast with the blood pressure record-

ings, the circadian rhythmicity of the heart ratewas preserved in all tetraplegic and paraplegicpatients. The patients with complete tetraple-gia (heart rate 71-1(17-7) to 60-4 (11-4) bpm)as well as the patients with incompletetetraplegia (heart rate 83-2 (13.2) to 68-1(10-6) bpm) showed a significant (P < 0 001)reduction in heart rate during the night period.Therefore, the results ofABPM showed severedysfunction of the spinal sympathetic systemin patients with complete tetraplegia, whereasthe parasympathetic regulation was normal(because the circadian rhythmicity in heartrate is controlled by the extraspinal vagalnerve).Of those patients presenting symptoms of

autonomic dysreflexia 70% (nine of 13) exhib-ited pathological ABPM recordings. The lossof circadian rhythmicity of blood pressure wasassociated with the occurrence of autonomicdysreflexia in 91% (12 of 13) of patients. Ofthose patients with pathological SSR poten-tials 27% (three of 11) still showed normalABPM measurements.

URODYNAMIC EXAMINATIONDuring urodynamic examination, which wascombined with continous monitoring of theblood pressure and heart rate, no paraplegicpatient (level of spinal cord injury < T6), but59% (13 of 22) of the tetraplegic patients dis-played signs of autonomic dysreflexia. Of thepatients with clinically complete tetraplegia

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476

180 A

140 -

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60

200

160

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80

40

14 16 18 20 22 2 4 6 8 10 12 14

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Figure 2 (A) NormalABPM measurements with a preserved physiological drop of b,

pressure during the night period (midnight to 0400). (B) Recordings from a patient wi

complete tetraplegia and multiple episodes of autonomic dysreflexia. (C) Recordings frc

the same patient after effective treatment of autonomic dysreflexia with the

antihypertensive drug nifedipine. Note that there is still a loss of the circadian regulatic

blood pressure.

(ASIA classification) 91% (10 of 11) an

those with incomplete tetraplegia 27% (t

of 11) showed signs of autonomic dysreflDuring urodynamic examination t

Table 2 Changes in systolic (SBP) and dystolic (DBP) blood pressures and heart rc

(HR) in patients with signs of autonomic dysreflexia during urodynamic examination

Basic DysreflexiaAbs

Cardiovascular values mean (SD) mean (SD) Difference (%) diffe

SBP (mm Hg) 115 (17) 155 (32) 355 40 (

DBP (mm Hg) 64 (13) 82 (16) 31i2 17 (

HR (bpm) 59 (6) 53 (10) -14 3 8

p < 001i.

patients showed episodes with significant(P < 0 001) increases of systolic and diastolicblood pressures of over 30% (table 2) and a

concurrent significant reduction of the heart

rate of about 15% (P < 0-01). Signs of auto-

nomic dysreflexia were induced by bladderdistension and were related mainly to hyper-reflexive bladder contractions and detrusor-sphincter dyssynergia. Only 62% (eight of 13)

of the patients had clinical symptoms of auto-

nomic dysreflexia.

Discussiont Tetraplegic patients and patients with a high

level of thoracic spinal cord injury (> T 6) are

prone to develop autonomic dysreflexia, whichis an autonomic failure due to the loss of

supraspinal control of spinal sympatheticcentres below the level of lesion.26 After recov-ering from spinal shock the remaining sym-

pathetic spinal centres can become

hyperreflexive such that non-specific stimulibelow the level of lesion can provoke uncon-trolled, excessive sympathetic outflow with

subsequent cardiovascular effects.4 The most

effective stimulus to provoke such hyperreflex-ive sympathetic activity below the level of

lesion seems to be bladder distension.' In

patients with spinal cord injury the enhancedsympathetic activity due to bladder stimula-tion could be shown by recording SSR poten-tials during urodynamic examination.27

In the present study SSR potentials were

recorded in patients with spinal cord injury to

test the function of the descending spinal sym-

pathetic tract. In accordance with studies per-- formed in other spinal cord diseases the

technique used here allows the assessment of

the degree to which supraspinal control of the

spinal sympathetic system is impaired.2892 Thefindings show that a loss of or impaired spinalsympathetic control is related to the develop-ment of autonomic dysreflexia. No patientwith preserved SSR potentials showed auto-

nomic dysreflexia symptoms either clinically or

during urodynamic examination. By contrast,all patients with autonomic dysreflexia symp-toms had pathological SSR. This fits in with

lood the finding that in three tetraplegic patientsith with incomplete lesions of the somatic nervous9m system (motor and sensory functions), but

in of complete disconnection of the autonomicspinal centres (abolished SSR potentials after

supralesional stimulation) displayed typicalsigns of autonomic dysreflexia during urody-

d of namic examination. Therefore, autonomic

hree failure can be assessed by the recording of SSR

exia. potentials, even when they are not clinically

:hese evident.The influence of the descending spinal sym-

pathetic tract on the cardiovascular system can

zte also be assessed using ABPM recordings.26 Bycontrast with healthy subjects and both para-

olute plegic and patients with incomplete tetra-

,rence plegia, almost all patients with complete

~25) tetraplegia showed a loss of physiological regu-

(16) lation of circadian blood pressure. This is con-(6) sistent with findings from patients with pure

autonomic failure, who also show a loss of cir-

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Assessment of autonomic dysreflexia in patients with spinal cord injury

cadian rhythmicity of blood pressure.30 Bycontrast with the impaired circadian rhythmic-ity of blood pressure in patients with completetetraplegia, the regulation of the circadianheart rate rhythmicity was preserved. This isdue to the fact that the this regulation is underthe control of the vagus nerve.'2

Nevertheless one third of patients lackingSSR had a preserved rhythmicity of physiolog-ical circadian blood pressure and only abouttwo thirds of patients with typical signs ofautonomic dysreflexia during urodynamicexamination showed a loss of the physiologicalcircadian blood pressure regulation. Thesefindings indicate that blood pressure regula-tion is more resistant to impairment after dis-connection of the spinal sympathetic centres.However, the ABPM recordings are useful inrecording the frequency and severity ofepisodes of autonomic dysreflexia during dailyliving. Furthermore, the effectiveness of med-ical (antihypertensive drugs) and surgical(sphincterotomy) treatment of these patientscan be monitored using ABPM recordings.2'Urodynamic examination can be regarded

as an effective and standardised diagnosticprocedure for evoking signs of autonomic dys-reflexia. In this study it was clear that urody-namic examination is a very sensitive tool inthe diagnosis of autonomic dysreflexia, as onlyhalf of the patients who showed signs of auto-nomic dysreflexia during urodynamic exami-nation presented clinical symptoms ofautonomic dysreflexia. As described earlier25 31episodes of autonomic dysreflexia during uro-dynamic examination were characterised byincreases of both systolic and diastolic bloodpressures by about 30%, while the heart ratedecreased by about 15%. Therefore, therecording of cardiovascular variables duringurodynamic examinations is important toassess signs of autonomic dysreflexia.

ConclusionIn patients with spinal cord injury autonomicfailure due to the impaired function of thespinal sympathetic tract can be assessed by dif-ferent techniques. The SSR recordings are themost sensitive at indicating the degree of dam-age of the descending spinal sympatheticsystem. The combination of urodynamicexaminations and ABPM recordings allowsthe prediction of the occurrence and severityof autonomic failure (sympathetic disconnec-tion). Therefore, early diagnosis and treatmentof autonomic dysreflexia, one of the most seri-ous complications in patients with a high level(> T6) of spinal cord injury, becomes possi-ble.

This work was supported by grants from the Swiss NationalScience Foundation (No 31-42899-95) and the InternationalResearch Institute for Paraplegia (P16/93).

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