Pancerebellar syndrome in heat stroke: clinical course and CT scan findings

Assessment of Heat Stroke-Induced Brain Injury: A Preclinical Study with a Rat Model Using 18F-FDG Brain PET

PURPOSE

Heat stroke is the most serious heat-related illness and is recognized as a worldwide public concern as global temperatures continue to rise. Although the clinical neurological complications of heat stroke are relatively well described, a limited number of studies exist that document imaging findings. Therefore, in this preclinical study, we aimed to identify the imaging findings of 18F-FDG brain PET following heat stroke and elucidate the utility of FDG PET in the evaluation of heat stroke-induced brain injury.

METHODS

Heat stroke was induced in Sprague Dawley rats by placing them in a hot and humid chamber maintained without food and water until they exhibited the heat stroke onset diagnostic criterion. Three hours after the induction ended, 18F-FDG brain PET images were acquired in 7 controls and 14 rats with heat stroke. Between groups, region-based (standardized uptake values were normalized to the whole brain and SUV of the whole brain (SUVWB), and voxel-based analyses were performed.

RESULTS

Of the 14 rats with heat stroke, 8 survived, whereas 6 did not. In the region-based and voxel-base analyses, the rats that did not survive showed significantly higher SUVRHB in the hypothalamus and significantly lower SUVRHB in several cortical regions than the controls as well as the survived rats. In the region-based analysis, the survived rats showed a significant increase or decrease in SUVRHB compared to the controls in a few cortical regions. However, no difference was observed in the voxel-based analysis.

CONCLUSIONS

The 3-h post-injury PET scan showed a distinctly different regional distribution of 18F-FDG in the brains of lethally injured heat stroke rats compared to the controls as well as the survived rats. The 18F-FDG brain PET may have the potential to provide early indicators of catastrophic injury and reflect the early neurological pathophysiology of heat stroke.

Identification of therapeutic targets in a murine model of severe exertional heat stroke

Exertional heat stroke (EHS) is a potentially lethal condition resulting from high core body temperatures (TC) in combination with a systemic inflammatory response syndrome (SIRS) with varying degrees of severity across victims, and limited understanding of the underlying mechanism(s). We established a mouse model of severe EHS to identify mechanisms of hyperthermia/inflammation that may be responsible for organ damage. Mice were forced to run on a motorized wheel in a 37.5°C chamber until loss of consciousness and were either removed immediately (exertional heat injury or EHI; TCMax = 42.4 ± 0.2°C) or remained in the chamber an additional 20 min (EHS; TCMax = 42.5 ± 0.4°C). Exercise control mice (ExC) experienced identical procedures to EHS at 25°C. At 3 h post-EHS, there was evidence for an immune/inflammatory response as elevated blood chemokine [interferon γ-induced protein 10 (IP-10), keratinocytes-derived chemokine (KC), macrophage inflammatory proteins (MIP-1α), MIP-1β, MIP-2] and cytokine [granulocyte colony-stimulating factor (G-CSF), interleukins (IL-10), IL-6] levels peaked and were highest in EHS mice compared with EHI and ExC mice. Immunoblotting of organs susceptible to EHS damage indicated that several kinases were sensitive to stress associated with heat/inflammation and exercise; specifically, phosphorylation of liver c-Jun NH2-terminal kinase (JNK) at threonine 183/tyrosine 185 immediately (0 h) postheating related to heat illness severity. We have established a mouse EHS model, and JNK [or its downstream target(s)] could underlie EHS symptomatology, allowing the identification of molecular pathways or countermeasure targets to mitigate heat illness severity, enable complete recovery, and decrease overall EHS-related fatalities.

Nanodelivery of traditional Chinese Gingko Biloba extract EGb-761 and bilobalide BN-52021 induces superior neuroprotective effects on pathophysiology of heat stroke

Military personnel often exposed to high summer heat are vulnerable to heat stroke (HS) resulting in abnormal brain function and mental anomalies. There are reasons to believe that leakage of the blood-brain barrier (BBB) due to hyperthermia and development of brain edema could result in brain pathology. Thus, exploration of suitable therapeutic strategies is needed to induce neuroprotection in HS. Extracts of Gingko Biloba (EGb-761) is traditionally used in a variety of mental disorders in Chinese traditional medicine since ages. In this chapter, effects of TiO2 nanowired EGb-761 and BN-52021 delivery to treat brain pathologies in HS is discussed based on our own investigations. We observed that TiO2 nanowired delivery of EGb-761 or TiO2 BN-52021 is able to attenuate more that 80% reduction in the brain pathology in HS as compared to conventional drug delivery. The functional outcome after HS is also significantly improved by nanowired delivery of EGb-761 and BN-52021. These observations are the first to suggest that nanowired delivery of EGb-761 and BN-52021 has superior therapeutic effects in HS not reported earlier. The clinical significance in relation to the military medicine is discussed.

Heat stroke induced cerebellar dysfunction: A “forgotten syndrome”

We report a case of heat stroke induced acute cerebellar dysfunction, a rare neurological disease characterized by gross cerebellar dysfunction with no acute radiographic changes, in a 61 years old ship captain presenting with slurred speech and gait ataxia. A systematic review of the literature on heat stroke induced cerebellar dysfunction was performed, with a focus on investigations, treatment and outcomes. After review of the literature and detailed patient investigation it was concluded that this patient suffered heat stroke at a temperature less than that quoted in the literature.

Symmetric bilateral caudate, hippocampal, cerebellar, and subcortical white matter MRI abnormalities in an adult patient with heat stroke

Heat stroke is the end result of excess heat stress and results in multiorgan dysfunction with a propensity for central nervous system (CNS) injury. Damage to the CNS appears to be the result of multiple mechanisms, including direct heat damage and the initiation of a sepsis-type syndrome. Only a few scattered case reports exist in the literature that document CNS damage via imaging. We present a case with symmetric bilateral magnetic resonance findings in the caudate nuclei, subcortical white matter, hippocampi, and cerebellum. To our knowledge, this is the first case to report symmetric bilateral caudate abnormality and bilateral hippocampal enhancement.

Clinical Recovery despite Cortical Cerebral and Cerebellar Damage in Heat Stroke

The prognosis of heat stroke has considerably improved with a mortality rate drop to 10% when therapeutic measurements including external cooling and aggressive rehydration are adopted. The role of imaging in predicting prognosis is uncertain. Some noted that development of cortical cerebellar atrophy is associated with development of a pancerebellar syndrome, while others suggested that evidence of cerebral cortical damage due to hypoxic-ischemic injury implies a poor prognosis. We observed a 17-year-old female who presented with lost of consciousness and seizure while jogging on a hot summer day followed by multi-organ failure. Brain MRI revealed a symmetric area of T2 hyperintensity and decreased diffusion in the cortical gyri of the frontal lobes. The patient made a complete recovery. MRI two years later showed disappearance of signal changes in the frontal cortex, but progressive atrophy of the cerebellum which was clinically silent. Our observation challenges the view of a close correlation between the imaging findings and prognosis in heat stroke.

[An acute severe heat stroke patient showing abnormal diffuse high intensity of the cerebellar cortex in diffusion weighted image: a case report]

A 47-year-old man was admitted to the hospital because of general convulsion, loss of consciousness and hyperthermia. A diagnosis of acute heat stroke was made clinically and neuroradiologically. As the consciousness level ameliorated, he developed severe abulia and mutism, then cerebellar ataxic syndrome (viz. truncal ataxia, hypermetria, ataxic speech and nystagmus). An MRI (diffusion weighted image; DWI) disclosed abnormal diffuse high signal intensity of the cerebellar cortex with reduced apparent diffusion coefficient (ADC). Two months later after the onset, truncal ataxia and dysarthria significantly improved, while dysmetria of the extremities rather worsened. At that time, the abnormal signal intensity of the cerebellar cortex disappeared, and the cerebellum became atrophic. The cerebellar blood flow was significantly decreased on brain SPECT (99mTc-ECD). The abnormal DWI signal intensity of the cerebellar cortex in the present patient may represent the cytotoxic edema of Purkinje cells resulting from heat stroke-related hyperthermia It is essential to repeat MRI examination for cerebellar pathology and to obtain better insight into sequelae in patients with acute heat stroke. Protirelin tartrate seemed to be valid for improvement of abulia in the present patient. Further study is indicated.

Diffusion-weighted magnetic resonance imaging of a severe heat stroke patient complicated with severe cerebellar ataxia

A 78-year-old woman was admitted for severe heat stroke with brain damage. She was unconscious on arrival at the emergency room. Her armpit temperature was 42.0 degrees C and blood pressure was 76/25 mmHg. She was rapidly cooled and given intensive treatment. On magnetic resonance imaging, T1- and T2-weighted images showed no significant signals, but diffusion-weighted images demonstrated localized symmetrical injuries of the cerebellum and thalami. She gradually became conscious, but severe cerebellar ataxia persisted.

Ataxias

Gait disorders in elderly individuals are a major cause of falls and their attendant morbidities. Ataxia is one of the neurologic components of fall risk, as are inattention or confusion, visual impairment, vestibular impairment, subcortical white matter disease, parkinsonism, weakness, sensory loss, orthostasis or arrhythmia with alterations in blood pressure, pain, medication use, and environmental hazards. Ataxia in the geriatric population has many causes. Correctly identifying them can improve clinicians' ability to offer treatment and management strategies to patients and their families. The goals should be safe mobility and preserved activities of daily living.

[Peripheral polyneuropathy after heat stroke]

The authors report the case of a woman who developed a peripheral polyneuropathy after heat stroke. All the classical aetiologies of neuropathy were excluded. The final diagnostic was residual peripheral neuropathy provoked by heat stroke. The sequella of heat stroke are dominated by cerebellar compromise, but this case shows that peripheral polyneuropathies exist even if they are rare. They raise the issue of care because of severe neurological sequella.

Brain damage after heat stroke

Cerebellar syndromes and radiologic cerebellar atrophy after hyperpyrexia have occasionally been reported, mostly in neuroleptic malignant syndromes, but neuropathologic studies are extremely rare. We studied 3 patients (a 74-year-old woman, a 63-year-old man, and an 80-year-old man) who had heat stroke during heat waves in France. One patient had generalized seizures and died 28 hours after admission. The other patients survived one month and 2 months after admission; both had palatal myoclonus, and in one case, magnetic resonance imaging showed high signal intensity in the cerebral peduncles. The main neuropathology in the 3 cases was severe diffuse loss of Purkinje cells associated with heat shock protein 70 expression by Bergmann glia. In situ end labeling was negative in surviving Purkinje cells, suggesting that the mechanism of neuronal death was not apoptosis. Degeneration of Purkinje cells axons resulted in myelin pallor of the white matter of the folia and of the hilum of the dentate nuclei. DNA internucleosomal breakages were identified by in situ end labeling in the dentate nuclei and centromedian nuclei of the thalamus and were associated with degeneration of the cerebellar efferent pathways: superior cerebellar peduncles, decussation of the superior cerebellar peduncles (Wernekinck commissure), and dentatothalamic tract. These findings suggest that the mechanisms of neuronal death in the dentate nuclei and centromedian nuclei of the thalamus was different from that in Purkinje cells and more likely resulted from deafferentation. Ammon's horn and other areas susceptible to hypoxia were spared. These observations confirm the selective vulnerability of Purkinje cells to heat-induced injury and involvement of the cerebellar efferent pathways in palatal myoclonus.

Downbeat nystagmus following classical heat stroke

Cerebellar syndrome following classical heat stroke is rare. We report a case of a 39-year-old man who presented with a cerebellar syndrome including downbeat nystagmus. MRI taken after 3 days of admission was normal. The downbeat nystagmus lasted for 6 days and than gradually disappeared. The ataxia and dysmetria improved gradually over 2 months. A brain CT scan performed 3 months later revealed no cerebellar atrophy. This case is unique as there were no predisposing factors (e.g. hypomagnesemia) and follow-up revealed complete reversibility of the ophthalmological abnormality. It reveals that the vestibulocerebellum is particularly vulnerable to thermal injury.

Inflammatory, hemostatic, and clinical changes in a baboon experimental model for heatstroke

The mortality and neurological morbidity in heatstroke have been attributed to the host's inflammatory and hemostatic responses to heat stress, suggesting that immunomodulation may improve outcome. We postulated that an experimental baboon model of heatstroke will reproduce human responses and clinical outcome to allow testing of new therapeutic strategies. Eight anesthetized juvenile baboons (Papio hamadryas) were subjected to heat stress in an incubator maintained at 44-47 degrees C until rectal temperature attained 42.5 degrees C (moderate heatstroke; n = 4) or systolic arterial pressure fell to <90 mmHg (severe heatstroke; n = 4) and were allowed to recover at room temperature. Four sham-heated animals served as a control group. Rectal temperature at the end of heat stress was 42.5 +/- 0.0 and 43.3 +/- 0.1 degrees C, respectively. All heat-stressed animals had systemic inflammation and activated coagulation, indicated by increased plasma IL-6, prothrombin time, activated partial thromboplastin time, and D-dimer levels, and decreased platelet count. Biochemical markers and/or histology evidenced cellular injury/dysfunction: plasma levels of thrombomodulin, creatinine, creatine kinase, lactic dehydrogenase, and alanine aminotransferase were increased, and varying degrees of tissue damage were present in liver, brain, and gut. No baboon with severe heatstroke survived. Neurological morbidity but no mortality was observed in baboons with moderate heatstroke. Nonsurvivors displayed significantly greater coagulopathy, inflammatory activity, and tissue injury than survivors. Sham-heated animals had an uneventful course. Heat stress elicited distinct patterns of inflammatory and hemostatic responses associated with outcome. The baboon model of heatstroke appears suitable for testing whether immunomodulation of the host's responses can improve outcome.

Postural stability and neurobehavioural effects of heat exhaustion among adult men

The medical complications of heat disorders, including haematological, cardiovascular and renal damage, have been well documented. However, very little has been written on its neurological complications. The objective of this study was to assess the effects of heat exhaustion on postural stability and neurobehavioral functions of men. The study is prospective in design and spans a 3-year period. All soldiers who were diagnosed to have heat exhaustion (cases) from 1 March 1998 to 31 August 1998 were included in the study. For each case, a healthy soldier (matched for age, ethnicity, years of education and military vocation) was recruited to serve as control. Each subject had a neurobehavioral assessment by using the Swedish Performance Evaluation System (SPES), a computerized test battery. The postural stability of the subjects was assessed using a computerized postural sway system. Findings for 37 heat exhaustion cases and 37 controls revealed that cases had a significantly higher prevalence of neurasthenia symptoms compared to the controls. There were significant (small) differences between the cases and controls in the neurobehavioral tests of choice reaction time, digit span and some parts of colour word stress and logical series measures. Postural stability in the cases was significantly poorer when in the "eyes-closed" condition, compared with the controls. Men with heat exhaustion, studied 2 weeks after the acute episode, had significantly more symptoms of neurasthenia, poorer performance in short-term memory and slower reaction time. The cases (as a group) had significantly poorer postural stability.

Cerebellar ataxia following whooping cough

Bordetella pertussis (BP), the agent of whooping cough, has not been recognized so far as a cause of permanent cerebellar ataxia in human. We describe three patients who developed a disabling and permanent cerebellar syndrome soon after whooping cough. In two patients, diagnosis of BP infection was confirmed by culture of nasopharyngeal secretions. The infection occurred between the age of 13 and 15 years, with neurological symptoms beginning after a delay varying from 3 weeks to 3 months. In our three patients, the cerebellar syndrome was characterized by dysmetria of ocular saccades, scanning speech and ataxic gait. Brain MRI demonstrated a pancerebellar atrophy. The pathogenesis of this cerebellar degeneration is not established. Experimental studies have demonstrated that the cerebellum is particularly vulnerable to lymphocytosis-promoting factor (LPF), one of the exotoxins from BP. The mechanism of this toxicity might be a marked increase in the cellular levels of 3',5'cyclic guanosine monophosphate (cGMP). Since whooping cough is a bacterial exotoxin-mediated disease, this is the first report of a cerebellar syndrome triggered by a bacterial exotoxin.

Heat strokes: aetiopathogenesis, neurological characteristics, treatment and outcome

Heat stroke is a thermal insult to the cerebral thermoregulatory system controlling heat production and heat dissipation. The thermal insult may be environmental as in 'classic heat stroke' or endogenous as in 'exertional heat stroke' in joggers or runners. The insult will lead to a steady rise in body core temperature to 40 degrees C or more, exhaustion of sweating with hot dry skin and central nervous system disturbances ranging from confusion to deep coma. Multisystem insult will follow leading to a fatal outcome, if not diagnosed and treated promptly. Rapid evaporative cooling and support of vital organs are the essential factors in the management of this condition. If treated early, no sequelae results, however, pancerebellar syndrome and spastic or flaccid paraparesis have been described in a few cases. Limited sun exposure, proper use of sunscreens, adequate fluid and electrolyte replacement and acclimatization are the key factors for prevention. Despite appropriate prevention and prompt treatment, heat stroke is unlikely to be totally prevented, but the mortality has improved dramatically to less than 10%.

Cerebellar degeneration following neuroleptic malignant syndrome

A 55-year-old woman with a history of bipolar affective disorder developed hyperpyrexia, rigidity and depressed consciousness (neuroleptic malignant syndrome) after commencing neuroleptic therapy. On regaining consciousness, she was mute and had signs suggesting pancerebellar involvement. Hyperpyrexia, which is a cardinal feature of neuroleptic malignant syndrome, may have caused cerebellar damage. Neuroleptic malignant syndrome needs both early recognition and prompt treatment to obviate devastating complications.

Heat intolerance induced by antidepressants

A case in which prescription medications induced heat intolerance which led to heat stroke is presented. A subject who suffered from depression and was treated with fluoxetine HCL (prozac) and lithium carbonate was engaged in mild intermittent work for 4 hours under hot/dry climatic conditions (Ta = 37 degrees C, rh = 15%). The subject lost consciousness, was hyperthermic and suffered from disseminated intravascular coagulation. A year later residual cerebellar symptoms were still evident and severe atrophy of the cerebellar tissue was demonstrated in a CT scan. It is suggested that drug-induced heat intolerance was the predisposing factor that reduced the patient ability to sustain exercise-heat stress, and under the favorable environmental circumstances led to excessive heat accumulation which ultimately caused heat stroke. This is the first description, to our knowledge, of heat intolerance of a patient treated by a combination of fluoxetine and lithium carbonate.

Lithium and neuroleptics in combination: is there enhancement of neurotoxicity leading to permanent sequelae?

Neurotoxicity in relation to concomitant administration of lithium and neuroleptic drugs, particularly haloperidol, has been an ongoing issue. This study examined whether use of lithium with neuroleptic drugs enhances neurotoxicity leading to permanent sequelae. The Spontaneous Reporting System database of the United States Food and Drug Administration and extant literature were reviewed for spectrum cases of lithium/neuroleptic neurotoxicity. Groups taking lithium alone (Li), lithium/haloperidol (LiHal) and lithium/ nonhaloperidol neuroleptics (LiNeuro), each paired for recovery and sequelae, were established for 237 cases. Statistical analyses included pairwise comparisons of lithium levels using the Wilcoxon Rank Sum procedure and logistic regression to analyze the relationship between independent variables and development of sequelae. The Li and Li-Neuro groups showed significant statistical differences in median lithium levels between recovery and sequelae pairs, whereas the LiHal pair did not differ significantly. Lithium level was associated with sequelae development overall and within the Li and LiNeuro groups; no such association was evident in the LiHal group. On multivariable logistic regression analysis, lithium level and taking lithium/haloperidol were significant factors in the development of sequelae, with multiple possibly confounding factors (e.g., age, sex) not statistically significant. Multivariable logistic regression analyses with neuroleptic dose as five discrete dose ranges or actual dose did not show an association between development of sequelae and dose. Database limitations notwithstanding, the lack of apparent impact of serum lithium level on the development of sequelae in patients treated with haloperidol contrasts notably with results in the Li and LiNeuro groups. These findings may suggest a possible effect of pharmacodynamic factors in lithium/neuroleptic combination therapy.

Reversible cerebellar gait ataxia with postural tremor during episodes of high pyrexia

We describe five patients presenting with high fever and isolated cerebellar gait ataxia. In all these patients, neurological examination revealed dysmetria, intention tremor and postural tremor during sustained posture, all restricted to the legs. Brain MRI was normal. In four of these patients, the recording of leg tremor during sustained postures showed a 3-Hz frequency. Cerebellar gait ataxia resolved within 3-10 days. We suggest that the ataxic gait was due to a reversible dysfunction of the spinocerebellar part of the anterior lobe.

Isolated cerebellar dysarthria associated with a heat stroke

Patients presenting with heat stroke may develop an acute pancerebellar syndrome. A patient presenting with an isolated cerebellar dysarthria after a heat stroke is reported. The dysarthria lasted two weeks. An isolated cerebellar dysarthria has been previously described in lesions of the paravermal zone of the rostral cerebellum. It is suggested that this region of the cerebellum is particularly vulnerable to fever.

Post-heatstroke parkinsonism and cerebellar dysfunction

A case is presented of a 45-year-old woman who developed parkinsonism, cerebellar dysfunction, aphasia and flaccid paralysis secondary to heat stroke. Magnetic resonance imaging revealed irregular patchy areas of increased signal intensity in the white matter of both cerebral hemispheres and the left striatum, remaining unchanged over a follow-up period of two years. Cerebellar atrophy, while not seen on initial examination, was present on the follow-up study done one year later and became more marked after two years.

Animal models for heat stroke studies

Heat stroke is a medical emergency where quick diagnosis and management of victims are essential for positive prognosis. Several biochemical, physiological and hematological changes were observed in heat stroke. It seems that all of these changes are a consequence of induced tissue damage, or may have been a compensatory action by the body. Induction of hyperthermia and temperature measurement are important components in heat stroke studies to determine the stage of progression or regression of heat stroke. Several animal models have been established by investigators in heat related studies. Rats, dogs, monkeys, baboons, cows, rabbits, sheep and chicks have all been used in such studies that allow manipulation of exposure conditions and various designs of experiments. Amongst these species, rats, rabbits and sheep are the most suitable models because of their similarity to man in response to high temperature and in relation to their availability, cost and simplicity of handling. Such models may be used to study various pharmacological and biochemical parameters and functions concurrently. Further informations could also be obtained from isolated organ studies. The present review is to analyse and compare the available methodology for heat stroke studies.

Cerebellar degeneration in neuroleptic malignant syndrome: neuropathologic findings and review of the literature concerning heat-related nervous system injury

A selective subtotal cerebellar neuronal degeneration was found in a patient who died 4 1/2 months after suffering neuroleptic malignant syndrome (NMS), a rare, potentially fatal disorder associated with neuroleptic medications. It is suggested that the cerebellar neuronal degeneration in this case was due to hyperpyrexia, a cardinal clinical feature of NMS. Similar pathologic findings appear not to have been previously reported in NMS but have been described in heat-induced central nervous system (CNS) injury. The findings imply that a cerebellar syndrome might be encountered in patients who survive NMS complicated by a particularly high febrile course.