Amantadine to enhance readiness for rehabilitation following severe traumatic brain injury

Does amantadine improve cognitive recovery in severe disorders of consciousness after aneurysmal subarachnoid hemorrhage? A double-blind placebo-controlled study

BACKGROUND

Severe disorders of consciousness (sDoC) are a common sequela of aneurysmal subarachnoid hemorrhages (aSAH), and amantadine has been used to improve cognitive recovery after traumatic brain injury.

OBJECTIVE

This study evaluated the effect of amantadine treatment on consciousness in patients with sDoC secondary to aSAH.

METHODS

This double-center, randomized, prospective, cohort study included patients ≥ 18 years old with sDoC after aSAH from February 2020 to September 2023. Individual patient data of patients were pooled to determine the effect of amantadine, in comparison to placebo. The primary outcomes at 3 and 6 months after the ictus were evaluated using the modified Rankin scale (mRS) and Glasgow outcome scale (GOS). In addition to all-cause mortality, secondary endpoints were assessed weekly during intervention by scores on Rappaport's Disability Rating Scale (RDRS) and Coma Recovery Scale-Revised (CRSR).

RESULTS

Overall, 37 patients with sDoC and initial Glasgow Coma Scale (GCS) varying between 3 and 11 were recruited and randomized to amantadine (test group, n = 20) or placebo (control group, n = 17). The average age was 59.5 years (28 to 81 year-old), 24 (65%) were women, and the mean GCS at the beginning of intervention was 7.1. Most patients evolved to vasospasm (81%), with ischemia in 73% of them. The intervention was started between 30 to 180 days after the ictus, and administered for 6 weeks, with progressively higher doses. Neither epidemiological characteristics nor considerations regarding the treatment of the aneurysm and its complications differed between both arms. Overall mortality was 10.8% (4 deaths). During the study, four patients had potential adverse drug effects: two presented seizures, one had paralytic ileus, and another evolved with tachycardia; the medication was not suspended, only the dose was not increased. At data opening, 2 were taking amantadine and 2 placebo.

CONCLUSION

Despite some good results associated with amantadine in the literature, this study did not find statistically significant positive effects in cognitive recovery in patients with delayed post-aSAH sDoC. Further large randomized clinical trials in patients' subgroups are needed to better define its effectiveness and clarify any therapeutic window where it can be advantageous.

Pharmacologic Therapies to Promote Recovery of Consciousness

Pharmacologic interventions are commonly used to support rehabilitation efforts of patients with disorders of consciousness (DoC). The 2018 practice guidelines recommend amantadine in adults with traumatic DoC to promote functional recovery, though several other stimulants are used off-label in clinical practice and trials, such as methylphenidate, bromocriptine, levodopa, and zolpidem. Differences in the mechanisms of action, adverse effects, pharmacokinetics, and drug-drug interactions should be considered when selecting the best agent for each individual patient. Overall, pharmacologic stimulants may provide a safe and inexpensive pathway to increased functionality and participation in rehabilitation. This article provides a concise summary of scientific evidence supporting the use of pharmacologic therapies to stimulate recovery of consciousness in patients with DoC.

Assessment of the effect of amantadine in patients with traumatic brain injury: A meta-analysis

BACKGROUND

Traumatic brain injury is a global burden. We aimed to perform a meta-analysis to determine the efficacy of amantadine for cognitive performance after traumatic brain injury.

METHODS

The systematic review was prospectively registered on the International Prospective Register of Systematic Reviews website under the registration number CRD42017080044. We used Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines to report the steps of meta-analysis. The search included electronic databases (PubMed, PsycINFO, Embase, Cochrane Library databases, CENTRAL, ProQuest and ClinicalTrials.gov trial registry). Critical care medicine journals and clinical neurology specialty were searched using www.scimagojr.com. There was no publication date restriction. Two authors assessed studies' relevance and extracted data. Studies were assessed for quality using the Cochrane risk of bias tool. Data were analyzed using Comprehensive Meta-analysis Program versions 2.0 and 3.0.

RESULTS

Twenty-six studies out of 3,440 records were included in the systematic review, of which only 14 clinical trials and 6 observational studies were included in the meta-analysis. Amantadine significantly enhanced the cognitive function relative to control group (mean difference [MD], 0.50; 95% confidence interval [CI], 0.33-0.66; p < 0.001, 16 studies, 1,127 participants, low certainty evidence). Consistent significant difference in favor of amantadine relative to control group was found (MD of 0.79 [95% CI, 0.34-1.24], very low certainty evidence, for cohort studies vs. MD of 0.40 [95% CI, 0.25-0.56], moderate certainty evidence, for RCTS). Starting amantadine in the first week after TBI had a significant effect on improving cognitive function (MD, 0.97; 95% CI, 0.45-1.49; 16 studies, 1,127 participants, low certainty). Amantadine showed a better effect when administered for less than 1 month (MD, 0.83; 95% CI, 0.56-1.11; low certainty) and to patients below 18 years of age (MD, 0.66; 95% CI, 0.32-0.99; low certainty) or to patients with less severe traumatic brain injury (MD, 0.40; 95% CI, 0.18-0.62; low certainty). No statistically significant difference existed between amantadine and the control concerning the adverse events (OR, 1.74; 95% CI, 0.88-3.44; p = 0.11, moderate certainty). Metaregression of the different clinical parameters, which are onset of treatment, age, and severity of traumatic brain injury, showed a statistically significant relation between onset of treatment and the effect size of amantadine. The relation between the other two parameters and the effect size of amantadine showed a marginal statistical significance.

CONCLUSION

Amantadine may improve the cognitive function when used after TBI. Further research with high validity is needed to reach a solid conclusion about the use of amantadine in traumatic brain injury.

LEVEL OF EVIDENCE

Systematic review/meta-analysis, level III.

Treating Traumatic Brain Injuries with Electroceuticals: Implications for the Neuroanatomy of Consciousness

According to the Centers for Disease Control and Prevention (CDC), traumatic brain injury (TBI) is the leading cause of loss of consciousness, long-term disability, and death in children and young adults (age 1 to 44). Currently, there are no United States Food and Drug Administration (FDA) approved pharmacological treatments for post-TBI regeneration and recovery, particularly related to permanent disability and level of consciousness. In some cases, long-term disorders of consciousness (DoC) exist, including the vegetative state/unresponsive wakefulness syndrome (VS/UWS) characterized by the exhibition of reflexive behaviors only or a minimally conscious state (MCS) with few purposeful movements and reflexive behaviors. Electroceuticals, including non-invasive brain stimulation (NIBS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS) have proved efficacious in some patients with TBI and DoC. In this review, we examine how electroceuticals have improved our understanding of the neuroanatomy of consciousness. However, the level of improvements in general arousal or basic bodily and visual pursuit that constitute clinically meaningful recovery on the Coma Recovery Scale-Revised (CRS-R) remain undefined. Nevertheless, these advancements demonstrate the importance of the vagal nerve, thalamus, reticular activating system, and cortico-striatal-thalamic-cortical loop in the process of consciousness recovery.

Amantadine: reappraisal of the timeless diamond-target updates and novel therapeutic potentials

The aim of the current review was to provide a new, in-depth insight into possible pharmacological targets of amantadine to pave the way to extending its therapeutic use to further indications beyond Parkinson's disease symptoms and viral infections. Considering amantadine's affinities in vitro and the expected concentration at targets at therapeutic doses in humans, the following primary targets seem to be most plausible: aromatic amino acids decarboxylase, glial-cell derived neurotrophic factor, sigma-1 receptors, phosphodiesterases, and nicotinic receptors. Further three targets could play a role to a lesser extent: NMDA receptors, 5-HT3 receptors, and potassium channels. Based on published clinical studies, traumatic brain injury, fatigue [e.g., in multiple sclerosis (MS)], and chorea in Huntington's disease should be regarded potential, encouraging indications. Preclinical investigations suggest amantadine's therapeutic potential in several further indications such as: depression, recovery after spinal cord injury, neuroprotection in MS, and cutaneous pain. Query in the database http://www.clinicaltrials.gov reveals research interest in several further indications: cancer, autism, cocaine abuse, MS, diabetes, attention deficit-hyperactivity disorder, obesity, and schizophrenia.

Neurophysiology and Treatment of Disorders of Consciousness Induced by Traumatic Brain Injury: Orexin Signaling as a Potential Therapeutic Target

BACKGROUND

Traumatic brain injury (TBI) can cause disorders of consciousness (DOC) by impairing the neuronal circuits of the ascending reticular activating system (ARAS) structures, including the hypothalamus, which are responsible for the maintenance of the wakefulness and awareness. However, the effectiveness of drugs targeting ARAS activation is still inadequate, and novel therapeutic modalities are urgently needed.

METHODS

The goal of this work is to describe the neural loops of wakefulness, and explain how these elements participate in DOC, with emphasis on the identification of potential new therapeutic options for DOC induced by TBI.

RESULTS

Hypothalamus has been identified as a sleep/wake center, and its anterior and posterior regions have diverse roles in the regulation of the sleep/wake function. In particular, the posterior hypothalamus (PH) possesses several types of neurons, including the orexin neurons in the lateral hypothalamus (LH) with widespread projections to other wakefulness-related regions of the brain. Orexins have been known to affect feeding and appetite, and recently their profound effect on sleep disorders and DOC has been identified. Orexin antagonists are used for the treatment of insomnia, and orexin agonists can be used for narcolepsy. Additionally, several studies demonstrated that the agonists of orexin might be effective in the treatment of DOC, providing novel therapeutic opportunities in this field.

CONCLUSION

The hypothalamic-centered orexin has been adopted as the point of entry into the system of consciousness control, and modulators of orexin signaling opened several therapeutic opportunities for the treatment of DOC.

Amantadine and memantine: a comprehensive review for acquired brain injury

This comprehensive review discusses clinical studies of patients following brain injuries (traumatic, acquired, or stroke), who have been treated with amantadine or memantine. Both amantadine and memantine are commonly used in the acute rehabilitation setting following brain injuries, despite their lack of FDA-approval for neuro-recovery. Given the broad utilization of such agents, there is a need to review the evidence supporting this common off-label prescribing. The purpose of this review is to describe the mechanisms of action for memantine and amantadine, as well as to complete a comprehensive review of the clinical uses of these agents. We included 119 original, clinical research articles from NCBI Medline, published before 2019. We focused on the domains of neuroplasticity, functional recovery, motor recovery, arousal, fatigue, insomnia, behavior, agitation, and cognition. Most of the existing research supporting the use of amantadine and memantine in recovery from brain injuries was done in very small populations, limiting the significance of conclusions. While most studies are positive; small effect sizes are usually reported, or populations are subject to bias. Furthermore, evidence is so limited that this review includes research regarding both acute and chronic acquired brain injury populations. Fortunately, reported short-term side effects generally are modest, and stop soon after amantadine/memantine is discontinued. However, responses are inconsistent, and the phenotype of responders remains elusive.

Noninvasive Neuromonitoring: Current Utility in Subarachnoid Hemorrhage, Traumatic Brain Injury, and Stroke

Noninvasive neuromonitoring is increasingly being used to monitor the course of primary brain injury and limit secondary brain damage of patients in the neurocritical care unit. Proposed advantages over invasive neuromonitoring methods include a lower risk of infection and bleeding, no need for surgical installation, mobility and portability of some devices, and safety. The question, however, is whether noninvasive neuromonitoring is practical and trustworthy enough already. We searched the recent literature and reviewed English-language studies on noninvasive neuromonitoring in subarachnoid hemorrhage, traumatic brain injury, and ischemic and hemorrhagic stroke between the years 2010 and 2015. We found 88 studies that were eligible for review including the methods transcranial ultrasound, electroencephalography, evoked potentials, near-infrared spectroscopy, bispectral index, and pupillometry. Noninvasive neuromonitoring cannot yet completely replace invasive methods in most situations, but has great potential being complementarily integrated into multimodality monitoring, for guiding management, and for limiting the use of invasive devices and in-hospital transports for imaging.

Amantadine Therapy in Traumatic Brain Injury Patients

Objective:

To review literature on amantadine therapy in patients with traumatic brain injury (TBI).

Data Sources:

MEDLINE (1966–March 2006), EMBASE (1974–March 2006), BIOSIS (1969–March 2006), and International Pharmaceutical Abstracts (1970–March 2006) were searched to identify papers on the clinical outcomes of patients with TBI treated with amantadine. A bibliographic search was also performed.

Study Selection and Data Extraction:

Papers were excluded if they were not published in English, if they included patients less than 16 years old, or if they included patients in whom the effects of multiple medications, rather than amantadine alone, were studied. Reports were categorized according to the time of initiation of amantadine following the injury.

Data Synthesis:

Reports examining early initiation of amantadine suggest a possible benefit for treatment of decreased responsiveness and functional recovery. One report examining late initiation of amantadine failed to demonstrate benefit in the treatment of motor impairment, while 2 reports suggested possible improvement of functional recovery. Finally, reports examining late initiation of amantadine in the treatment of cognitive and behavioral therapy demonstrated possible benefit.

Conclusions:

Further investigation is needed before either early or late initiation of amantadine can be recommended for treatment of decreased responsiveness and functional recovery. However, while additional research is conducted, late initiation of amantadine can be considered an option for the treatment of cognitive and behavioral impairments in patients with TBI.

Posttraumatic parkinsonism

Amantadine hydrochloride is one of the most commonly used drugs in the pharmacotherapeutic treatment of disorders of consciousness (DOCs) following traumatic brain injury (TBI). Indeed, its actions as a pro-dopaminergic drug and as an N-methyl-D-aspartate antagonist makes amantadine an interesting candidate to improve consciousness and responsiveness in individuals with DOC, including vegetative state and minimally conscious state. Giacino et al (N Engl J Med. 2012;366(9):819-826) recently reported that amantadine was able to accelerate the functional recovery course of subjects after TBI with DOC, during a 4-week treatment period. Some patients with DOC following severe TBI have been reported to have parkinsonian symptoms. Severe TBI and posttraumatic parkinsonism may share a common midbrain network dysfunction. In fact, both vegetative state and minimally conscious state following severe TBI can include features of akinetic mutism and parkinsonism. Responsiveness to pro-dopaminergic agents in some patients and to deep brain stimulation in others, might depend, respectively, on the integrity, or lack thereof, of the dopaminergic postsynaptic receptors. We are of the strong opinion that more attention should be given to parkinsonian findings in persons with DOC after severe TBI and would advocate for multicenter, randomized, controlled trials to assess risk factors for parkinsonism following severe TBI.

Clinical management of the minimally conscious state

The minimally conscious state (MCS) was defined as a disorder of consciousness (DoC) distinct from the vegetative state more than a decade ago. While this condition has become widely recognized, there are still no guidelines to steer the approach to assessment and treatment. The development of evidence-based practice guidelines for MCS has been hampered by ambiguity around the concept of consciousness, the lack of accurate methods of assessment, and the dearth of well-designed clinical trials. This chapter provides a critical review of existing assessment procedures, critically reviews available treatment options and identifies knowledge gaps. We close with practice-based recommendations for a rational approach to clinical management of this challenging population.

The promotion of recovery through rehabilitation after acquired brain injury in children

A degree of motor recovery is typically seen after acquired brain injury in children. The extent to which rehabilitation efforts can claim credit for this is disputed. Strong correlations between late impairment outcomes and early severity and impairment indices are seen both in adults and children. These correlations have been interpreted by some as evidence that recovery is largely intrinsic and that any additional rehabilitation effects are small. Such views are belied by published animal studies demonstrating the possibility of large rehabilitation effects. Animal models suggest that to achieve similar rehabilitation treatment effect sizes in clinical practice, rehabilitation 'doses' should be greater, rehabilitation efforts should start sooner, and premature accommodation of impairment should be avoided.

Therapeutic options to enhance coma arousal after traumatic brain injury: state of the art of current treatments to improve coma recovery

Traumatic brain injury is a leading cause of death and disability. Optimizing the recovery from coma is a priority in seeking to improve patients' functional outcomes. Standards of care have not been established: pharmacological interventions, right median nerve and sensory stimulation, dorsal column stimulation (DCS), deep brain stimulation, transcranial magnetic stimulation, hyperbaric oxygen therapy and cell transplantation have all been utilized with contrasting results. The aim of this review is to clarify the indications for the various techniques and to guide the clinical practice towards an earlier coma arousal. A systematic bibliographic search was undertaken using the principal search engines (Pubmed, Embase, Ovid and Cochrane databases) to locate the most pertinent studies. Traumatic injury is a highly individualized process, and subsequent impairments are dependent on multiple factors: this heterogeneity influences and determines therapeutic responses to the various interventions.

Methylphenidate and amantadine to stimulate reawakening in comatose patients resuscitated from cardiac arrest

BACKGROUND

Despite critical-care packages including therapeutic hypothermia (TH), neurologic injury is common after cardiac arrest (CA) resuscitation. Methylphenidate and amantadine have treated coma in traumatically-brain-injured patients with mixed success, but have not been explored in post-arrest patients.

OBJECTIVE

Compare the outcome of comatose post-arrest patients treated with neurostimulants to a matched cohort.

METHODS

Retrospective cohort study from 6/2008 to 12/2011 in a tertiary university hospital. We included adult patients treated with methylphenidate or amantadine after resuscitation from in-hospital or out-of-hospital CA (OHCA) of any rhythm, excluding patients with traumatic/surgical etiology of arrest, terminal re-arrest within 6h, or withdrawal of care by family within 6h. Primary outcome was following commands; secondary outcomes included survival to hospital discharge, cerebral performance category (CPC), and modified Rankin scale (mRS). We compared characteristics and outcomes to a control cohort matched on TH and 72 h FOUR score ± 1.

RESULTS

Of 588 patients, 8 received methylphenidate, 6 received amantadine, and 2 both. Most were female suffering OHCA with median age 61 years. All received TH and a multi-modal neurological evaluation. Initial exam revealed median GCS 6 and FOUR 7, which was unchanged at 72 h. Six patients (38%) followed commands prior to discharge at median 2.5 days (range: 1-18 days) after treatment. Patients receiving neurostimulants trended toward improved rate of following commands, survival to hospital discharge, and distribution of CPC and mRS scores.

CONCLUSIONS

Neurostimulants may be considered to stimulate wakefulness in selected post-cardiac arrest patients, but a prospective trial is needed to evaluate this therapy.

Biologic and plastic effects of experimental traumatic brain injury treatment paradigms and their relevance to clinical rehabilitation

Neuroplastic changes, whether induced by traumatic brain injury (TBI) or therapeutic interventions, alter neurobehavioral outcome. Here we present several treatment strategies that have been evaluated by using experimental TBI models and discuss potential mechanisms of action (ie, plasticity) and how such changes affect function.

Electrophysiological assessments of cognition and sensory processing in TBI: applications for diagnosis, prognosis and rehabilitation

Traumatic brain injuries are often associated with damage to sensory and cognitive processing pathways. Because evoked potentials (EPs) and event-related potentials (ERPs) are generated by neuronal activity, they are useful for assessing the integrity of neural processing capabilities in patients with traumatic brain injury (TBI). This review of somatosensory, auditory and visual ERPs in assessments of TBI patients is provided with the hope that it will be of interest to clinicians and researchers who conduct or interpret electrophysiological evaluations of this population. Because this article reviews ERP studies conducted in three different sensory modalities, involving patients with a wide range of TBI severity ratings and circumstances, it is difficult to provide a coherent summary of findings. However, some general trends emerge that give rise to the following observations and recommendations: 1) bilateral absence of somatosensory evoked potentials (SEPs) is often associated with poor clinical prognosis and outcome; 2) the presence of normal ERPs does not guarantee favorable outcome; 3) ERPs evoked by a variety of sensory stimuli should be used to evaluate TBI patients, especially those with severe injuries; 4) time since onset of injury should be taken into account when conducting ERP evaluations of TBI patients or interpreting results; 5) because sensory deficits (e.g., vision impairment or hearing loss) affect ERP results, tests of peripheral sensory integrity should be conducted in conjunction with ERP recordings; and 6) patients' state of consciousness, physical and cognitive abilities to respond and follow directions should be considered when conducting or interpreting ERP evaluations.

Parcellating the neuroanatomical basis of impaired decision-making in traumatic brain injury

Cognitive dysfunction is a devastating consequence of traumatic brain injury that affects the majority of those who survive with moderate-to-severe injury, and many patients with mild head injury. Disruption of key monoaminergic neurotransmitter systems, such as the dopaminergic system, may play a key role in the widespread cognitive dysfunction seen after traumatic axonal injury. Manifestations of injury to this system may include impaired decision-making and impulsivity. We used the Cambridge Gambling Task to characterize decision-making and risk-taking behaviour, outside of a learning context, in a cohort of 44 patients at least six months post-traumatic brain injury. These patients were found to have broadly intact processing of risk adjustment and probability judgement, and to bet similar amounts to controls. However, a patient preference for consistently early bets indicated a higher level of impulsiveness. These behavioural measures were compared with imaging findings on diffusion tensor magnetic resonance imaging. Performance in specific domains of the Cambridge Gambling Task correlated inversely and specifically with the severity of diffusion tensor imaging abnormalities in regions that have been implicated in these cognitive processes. Thus, impulsivity was associated with increased apparent diffusion coefficient bilaterally in the orbitofrontal gyrus, insula and caudate; abnormal risk adjustment with increased apparent diffusion coefficient in the right thalamus and dorsal striatum and left caudate; and impaired performance on rational choice with increased apparent diffusion coefficient in the bilateral dorsolateral prefrontal cortices, and the superior frontal gyri, right ventrolateral prefrontal cortex, the dorsal and ventral striatum, and left hippocampus. Importantly, performance in specific cognitive domains of the task did not correlate with diffusion tensor imaging abnormalities in areas not implicated in their performance. The ability to dissociate the location and extent of damage with performance on the various task components using diffusion tensor imaging allows important insights into the neuroanatomical basis of impulsivity following traumatic brain injury. The ability to detect such damage in vivo may have important implications for patient management, patient selection for trials, and to help understand complex neurocognitive pathways.

Amantadine treatment following traumatic brain injury in children

PRIMARY OBJECTIVE

The focus of this paper is to review the current literature on the use of amantadine in children who have sustained a head injury.

MAIN OUTCOMES AND RESULTS

A MEDLINE search was conducted and yielded five papers. They were composed of prospective, retrospective and case study designs. Dosage use and side effect profiles were consistent with expected norms. Efficacy was measures primarily by alertness and arousal and positive results were found for all studies on these dimensions. Behavioural and cognitive measures of outcome yielded mixed results.

CONCLUSIONS

The studies reviewed for this paper suggest that amantadine is clinically beneficial for children who have sustained head injuries. Double blind placebo controlled trials with larger sample sizes are needed to further substantiate these findings.

Persistent cognitive dysfunction after traumatic brain injury: A dopamine hypothesis

Traumatic brain injury (TBI) represents a significant cause of death and disability in industrialized countries. Of particular importance to patients the chronic effect that TBI has on cognitive function. Therapeutic strategies have been difficult to evaluate because of the complexity of injuries and variety of patient presentations within a TBI population. However, pharmacotherapies targeting dopamine (DA) have consistently shown benefits in attention, behavioral outcome, executive function, and memory. Still it remains unclear what aspect of TBI pathology is targeted by DA therapies and what time-course of treatment is most beneficial for patient outcomes. Fortunately, ongoing research in animal models has begun to elucidate the pathophysiology of DA alterations after TBI. The purpose of this review is to discuss clinical and experimental research examining DAergic therapies after TBI, which will in turn elucidate the importance of DA for cognitive function/dysfunction after TBI as well as highlight the areas that require further study.

Is there anybody in there? Detecting awareness in disorders of consciousness

The bedside detection of awareness in disorders of consciousness (DOC) caused by acquired brain injury is not an easy task. For this reason, differential diagnosis using neuroimaging and electrophysiological tools in search for objective markers of consciousness is being employed. However, such tools cannot be considered as diagnostic per se, but as assistants to the clinical evaluation, which, at present, remains the gold standard. Regarding therapeutic management in DOC, no evidence-based recommendations can be made in favor of a specific treatment. The present review summarizes clinical and paraclinical studies that have been conducted with neuroimaging and electrophysiological techniques in search of residual awareness in DOC. We discuss the medical, scientific and ethical implications that derive from these studies and we argue that, in the future, the role of neuroimaging and electrophysiology will be important not only for the diagnosis and prognosis of DOC but also in establishing communication with these challenging patients.

Pharmacotherapy to enhance arousal: what is known and what is not

Severe brain injury results in a disturbance among a wide range of critical neurotransmitter systems. Each neurotransmitter system places its own functional role while being interconnected to a multitude of other systems and functions. This chapter seeks to review the major neurotransmitter systems involved after severe acquired brain injury. While limited in their construct, animal models of brain injury have demonstrated agents that may assist in the recovery process and those that may further slow recovery. We review further the issue of laboratory evidence and what is transferable to the clinic. Lastly, this chapter reviews published clinical pharmacotherapy studies or trials in the arena of arousal for those with clinical severe brain injury. We discuss limitations as well as findings and present the available evidence in a table-based format. While no clear evidence exists to suggest a defined and rigid pharmacotherapeutic approach, interesting data does suggest that several medications have been associated with enhanced arousal. Several studies are underway or about to begin that will shed more light on the utility of such agents in improving function after severe brain injury. For now, clinicians must employ their own judgment and what has been learned from the limited literature to the care of a challenging group of persons.

Amantadine Enhancement of Arousal and Cognition After Traumatic Brain Injury

Objective:

To determine the role of amantadine therapy tor early arousal and improved cognition in traumatic brain injury (TBI).

Data Sources:

Literature was accessed through MEDLINE (1950–August 2007) using the MeSH terms amantadine, brain injuries, cognition, and arousal. PubMed (through August 2007) terms included amantadine, traumatic brain injury, and cerebral injury.

Study Selection and Data Extraction:

All studies ol amantadine (used <6 mo after injury) for enhancement of arousal or cognition in patients with TBI were reviewed.

Data Synthesis:

Many cases of TBI are associated with frontal lobe injury. As a dopamine agonist, amantadine is thought to be involved in frontal lobe stimulation. Two case reports, 3 retrospective studies, and 2 randomized, double-blind, controlled trials of amantadine therapy for early arousal in TBI were identified and reviewed. Limitations of the available studies include open design, retrospective design, and heterogeneous brain injury types. Results have been inconsistent between studies, largely due to variability in designs, heterogeneity in patient populations, time following injury, and use of numerous different outcome measures. Despite these limitations, improvements in arousal and cognition, as documented by the Glasgow Coma Scale and olher measures, have been observed in patients with TBI when amantadine has been initiated 3 days to 5 months after injury.

Conclusions:

At doses of 200–400 mg/day, amantadine appears to safely improve arousal and cognition in patients with TBI. Additional prospective controlled studies with homogeneous patient populations will better define the role of amantadine for early arousal.