Paul Reading Maurice Curtis, Andrew Naylor, Richard Faull ... - ACNR

Rehabilitation ArticleCurrent Understanding of Dysautonomia AfterSevere Acquired Brain InjuryDysautonomia is one of a number of names used todescribe a clinical syndrome affecting a subgroupof survivors of acquired brain injury (ABI). 1 Thesyndrome consists of paroxysmal elevations of autonomicnervous system (ANS) parameters, for example, heartrates (HR) up to 190 beats per minute, respiratory rates(RR) of 60 breaths per minute, temperatures to 42°C,arterial blood pressures (BP) of 170/120mmHg andsweating. These signs are accompanied by assorted formsof muscle overactivity such as decerebrate or decorticateposturing, dystonias, rigidity and spasticity.Traumatic brain injury (TBI) is the most commonlyreported causative condition, with an estimated incidenceof 8-15% in moderate and severe TBI admitted to an intensivecare unit (ICU). 2 There is no incidence data on otheraetiologies, although anecdotally dysautonomia appears tobe much rarer. Acute neurological events that have beenreported to precipitate dysautonomia include: spontaneoussubarachnoid or intracerebral haemorrhages, pressurefrom tumours, intra-aqueductal abscess, hydrocephalusand cerebral hypoxia in the absence of other trauma. 3In a prospective cohort study, 2 dysautonomic subjectshad a significantly worse outcome, a greater period ofhospitalisation and higher estimated costs compared tonon-dysautonomic survivors of TBI. However, dysautonomicand non-dysautonomic patients were found tohave a comparable degree of improvement with rehabilitation,albeit dysautonomic patients start at a lower pointand take longer to improve. 1There is considerable disparity between the estimatedincidence of dysautonomia in prospective research andthe quantity of scientific literature. There are a number ofplausible explanations for this discrepancy. The mostapparent difficulty is the proliferative and synonymousnature of the nomenclature, with at least 10 differentnames being used for the same condition. These includeparoxysmal sympathetic storms, autonomic dysfunctionsyndrome, acute midbrain syndrome, hypothalamic-midbraindysregulation syndrome, fever of central origin,hyperpyrexia associated with muscle contraction, dysautonomia,sympathetic or autonomic storming and paroxysmalautonomic instability with dystonia. 3Another explanation for the discrepancy is that dysautonomiais currently a diagnosis of exclusion and relies ona high index of suspicion. Firstly, some degree of autonomicarousal is a common feature during the early postacuterecovery from ABI and there is no clear thresholdwhere this activity should become classified as dysautonomia.Furthermore, dysautonomia shares a high degree ofoverlap with the presentation of common complicationssuch as opioid withdrawal, epileptic seizures, and sepsis,as well as rarer conditions such as neuroleptic malignantsyndrome, malignant hyperthermia and others. 3Natural history / clinical featuresAnalysis of the hospital course of post TBI dysautonomiasuggests that the syndrome follows a common three phasepattern. The first phase runs from admission to ICU tothe cessation of paralysis and/or sedation. There is little todifferentiate the dysautonomic and non-dysautonomicpatients in terms of physiological variables during thisstage. 1The second phase commences with the cessation of regularsedation. The dysautonomic patient will usually haveconsistently raised HR and temperature, and increasingregional muscle tone. Paroxysms of posturing and ANSoveractivity are superimposed on these elevated baselinelevels. In the early parts of this second phase, episodes arefrequent, prolonged and intense. Some episodes will beprovoked by identifiable stimuli (for example, pain, endotrachealsuctioning, passive movements such as turning,bathing and muscle stretching, constipation, a kinked urinarycatheter, emotional stimuli, as well as environmentalstimuli such as loud noises), 3 but others show no overtcause. The pattern of posturing is most often asymmetricaland may not fit into classical decorticate or decerebratepostures. 4 With increasing time post injury, the paroxysmsdecrease in duration, frequency and magnitude; restingBP, RR, HR and temperature return to normal. The patternof posturing may change, revealing an underlyingtetraplegia or other focal neurological deficit. Sweatingpatterns often alter, from whole body to upper trunk,head and neck, before ceasing entirely. 5 In the majority ofpatients, background muscle tone increases with variableflexor, extensor or mixed dystonias in the limbs, neck,trunk and facial muscles. The end of phase two is markedby the cessation of regular dysautonomic paroxysms.Extinguishment of episodes usually coincides withimproving neurological status, although most are left withsome degree of dystonia and spasticity. 1 The high degreeof physical disability can prevent voluntary muscle activity,limiting the accuracy of cognitive assessment.The final phase commences with the termination ofregular paroxysms, though by this stage, dysautonomiapatients with severe dystonia will have major deformitiesof joints and markedly reduced range of movement. 1Although ANS variables are within normal limits, noxiousstimuli may still provoke an episode for at least 14 monthspost injury. 6 Patients who develop a mechanism for communicationoften report persistent abnormal painfulresponses to normally non-noxious stimuli.ManagementPharmacological management is difficult and there is limiteddata available to guide decision-making. In the ICUsetting, widespread use of paralysis/sedation has beenshown to delay the onset of clinical features. 1 Anecdotally,the best available evidence for treatment efficacy includesbromocriptine, gabapentin and intrathecal baclofen(ITB). 7,8 Intravenous morphine and midazolam are effectivebut have problematic sedative effects. Drugs withsympathetic activity (particularly clonidine, propanololand labetolol) are also commonly used; however there aresuggestions that these drugs treat the symptoms ratherthan the underlying disease process. Equally, there is noevidence that anticonvulsants other than gabapentin areeffective in this condition. The potential to trigger paroxysmsvia noxious stimuli has led one author to suggestpre-treatment in this context. 9The rehabilitation management of dysautonomia centreson the usual approach of minimising unnecessarydisability and complications while maximising the potentialfor the individual to regain a maximal quality of life.In the rehabilitation setting, this includes adequate fluids,nutrition, and spasticity management including splinting,serial casting and pressure area management. Given thecombination of spasticity and nociception, ITB is increasinglybeing used earlier in the management.Clinical significanceThere are a variety of reasons to believe that dysautonomiawarrants active management. A lack of early recognitionIain E Perkes is enrolled in B Medand B Med Sci at the University ofNewcastle, Australia. He is alsoemployed as a Research Assistantby the Division of Anaesthesia,Cambridge University. His previousposts include Research Officerat: the NSW Centre for HealthResearch in Criminal Justice, theNational Centre in HIV SocialResearch at the University of NewSouth Wales, and the School ofPublic Health, University ofSydney. His primary researchinterest is traumatic brain injury.Ian J Baguley is a Senior StaffSpecialist and Research TeamLeader of Westmead Hospital’sBrain Injury RehabilitationService and a Clinical SeniorLecturer in the Department ofRehabilitation Medicine at theUniversity of Sydney. Dr Baguleyregularly reviews for professionaljournals and research fundingbodies and has authored manypublications in various fields ofRehabilitation Medicine. His principalresearch interests includetraumatic brain injury and spasticityrehabilitation.Correspondence to:Dr Ian J Baguley,Brain Injury RehabilitationService,Westmead Hospital,Westmead, NSW 2145, Australia.Tel. (612) 9845 7941Fax. (612) 9635 8892Email. ianb@biru.wsahs.nsw.gov.au10 I ACNR • VOLUME 8 NUMBER 1 • MARCH/APRIL 2008