| Part OneMRI Findings of Brain After Heat Stroke ABSTRACTObjective:Heat stroke (HS) is characterized by an elevated core body temperature over 40℃ and neurologic abnormalities including delirium, seizures, or coma. Potential immediate complications of severe heat stroke include shock, acute respiratory distress syndrome, acid-base or electrolyte disturbances, disseminated intravascular coagulation and rhabdomyolysis. Heat stroke is generally reported in case reports or small patients series. This paper tries to investigate the MR findings of brain after heat stroke. To assess the role of susceptibility-weighted imaging in the detection of intracranial hemorrhage after heat stroke and in the prognosis.Methods:Eight cases of patients diagnosed heat stroke by clinical methords were selected with inclusion criterias as follows: ①With the incidence of working or living outdoor during high temperature environment; ② With high fever and coma. Exclusion criterias:①Oganophosphorus pesticide poisoning;②Food poisoning; ③Encephalitis; ④Bacillary dysentery; ⑤Malaria;⑥Boxic pneumonia. All the eight patients appeared high fever (40℃-42℃) and coma (Glasgow Coma Scale 3-9) during outdoor activities or labor in summer heat waves, and other diseases were excluded by clinical and laboratory examinations. The MR studies including Ti-weighted imaging, T2-weighted imaging, T2-fluid attenuated inversion recovery, diffusion weighted imaging and susceptibility weighted imaging were performed within 2-5 days after heat stroke by a SIEMENS Avanto 1.5 T magnetic resonance scanner with a standard quadrature eight channel head coil. The MR protocol included the standard structural sequences T1-weighted (TR 450ms, TE 15ms), T2-weighted(TR 3000ms, TE 100ms), diffusion-weighted (TR 3100ms, TE 99ms, b value:0 and 100), slice thickness 5mm, interlamellar spacing 1.5mm, and FLAIR (TR 8000ms, TE 120ms). Imaging parameters of susceptibility-weighted imaging were as follows: TR 49ms, TE 40ms, slice thickness 2mm, interlamellar spacing 0.4mm, FOV 230mm X 230mm2.Five patients were followed up by the same MR studies with 2-4 times. All patients were divided into two groups according to whether hemorrhage was detected or not by susceptibility-weighted imaging. The number of deaths and survivals were counted respectively. Statistical analysis was performed by the Statistical Package for the Social Sciences (SPSS, version 17). Fisher’s exact test was performed to compare the differences. The differences were considered statistically significant when P<0.05.Results:Among eight cases with heat stroke, five patients were detected abnormal signals which located at brain stem, cerebellar dentate nucleus, cerebellum feet, cerebellum, hippocampus, corona radiate, semi oval center and right frontal-temporal-parietal lobe. The lesions including micro hemorrhage, cytotoxic edema, vasogenic edema, hemorrhagic infarction, encephalitis. Symmetrical distribution were displayed for cerebellar lesions.Punctate hemorrhages were detected in brain stem, corona radiata and frontal lobe by susceptibility-weighted imaging for three patients. Among the three cases, two patients came to death in the 5th day and the 25th day after heat stroke respectively. Another patient became a persistent vegetative state and died about 3 months later. Five patients with no hemorrhage detected gradually recovered and cerebellar dysfunction remained to various degrees. The number of deaths and survivals in two groups are shown in Table 3 based on that whether hemorrhage was detected or not. Case fatality rate had statistical differences in two groups (P=0.018).Conclusion:Heat stroke can cause cerebral lesions such as ischemia, hemorrhage, infarction and inflammation. DWI can be a sensitive sequence to discover early cytotoxic edema, SWI can be a sensitive sequence to detect intracranial micro hemorrhage. These lesions may be revealed by multiple complementary MRI sequences. MR findings have certain characteristics which often involved in the cerebellum symmetrically. Heat stroke is a life-threatening condition characterized by hyperthermia and accompanied by various complications such as disseminated intravascular coagulation. Susceptibility-weighted imaging is a very useful tool for detection of intracranial hemorrhage and may probably evaluate the prognosis after heat stroke.Part TwoDiffusion Tensor Imaging and Magnetic Resonance Spectroscopy of The Cerebellum In Patients After Heat Stroke ABSTRACTObjective:Both diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) are MR techniques that have recently been increasingly used in clinical practice. Since the cerebellum has selective vulnerability of Purkinje cells to heat-induced injury. This study tries to explore the application value of cerebellar diffusion tensor imaging in patients after heat stroke and to explore changes in metabolite levels of the cerebellum after heat stroke by magnetic resonance spectroscopy.Methods:Study group consisted of eleven patients after heat stroke admitted to Insentive Care Unit, with a score of 3 to 9 in Glasgow Coma Scale (GCS) and seven age matched healthy subjects recruited from the same summer heat waves. MR examinations were performed by a SIEMENS Avanto 1.5 T magnetic resonance scanner with a standard quadrature head coil. The MR protocol included the standard structural sequences T1-weighted (TR450ms, TE15ms), T2-weighted (TR3000ms, TE100ms), diffusion-weighted, and FLAIR imaging (TR8000ms, TE120ms). The imaging parameters for DTI (TENSOR 25,1000b) were as follows:TR9999ms, TE89.2ms, slice thickness 5.0, spacing,0.0. MR data processing was performed by using Functool, a program for the visualization and processing of DTI data. Fractional anisotropy (FA) values of cerebellar white and gray matter were measured for patients after heat stroke and normal controls. Four regions of interest (ROIs) were defined to measure the FA and ADC values:bilateral normal-appearing cerebellar white matter and gray matter. The criteria of normal appearing cerebellar white matter and gray matter was defined as areas with no abnormal signal revealed by routine MR sequences. Four patients with symmetrical cerebellar lesions were excluded.Multi-voxel chemical shift imaging was performed and the cerebellar metabolite ratios, involving N-acetyl aspartate/creatine ratio (NAA/Cr), N-acetyl aspartate/creatine2 ratio (NAA/Cr2), choline/creatine ratio (Cho/Cr), choline/creatine2 ratio (Cho/Cr2), N-acetyl aspartate/choline ratio (NAA/Cho), and NAA/(Cho+Cr) were estimated for eight patients after heat stroke and seven normal controls. A standard 2D CSI-PRESS (Chemical-shift imaging point-resolved spectroscopy) was used with the following parameters:TR=1500ms, TE=135ms, Fov 160×160mm2, Thickness 15mm, Average 4. A rectangular VOI (Volume of Interest) (A>>P 30mm, R>>L 70mm, F>>H 15mm) was placed to cover the cerebellum between the fourth ventricle and skull.The Mann-Whitney U test was performed to compare the differences of DTI and MRS parameters between the two groups. Pearson correlation of NAA/Cr and the Glasgow Coma Scale (GCS) of patients after heat stroke was analyzed. The dif-ferences were considered statistically significant when P<0.05.Results:The FA value of normal-appearing cerebellar white matter in patients after HS was found to be decreased compared to normal control subjects (652.5±86.1 vs 769.5±58.4, p=0.025). The FA value of normal-appearing cerebellar gray matter in patients after HS was found to be decreased compared to normal control subjects (158.8±27.9 vs 187.5±15.8, p=0.040). Howeve, there had no statistical difference for the ADC value of both normal-appearing cerebellar white and gray matter compared to normal control subjects (p>0.05). The ADC value of normal-appearing cerebellar white matter in patients after HS was found to be increased compared to normal control subjects (681.3±37.5 vs 666.1±33.6, p=0.406), The ADC value of normal-appearing cerebellar gray matter in patients after HS was found to be increased compared to normal control subjects (873.6±120.7 vs 790.1±83.7, p=0.142).The ratio of NAA/Cr in cerebellum after heat stroke was found to be significantly decreased compared to normal control subjects (0.79±0.10 vs 1.03±0.11, p=0.004). The ratio of Cho/Cr in cerebellum after heat stroke was found to be statistically decreased compared to normal control subjects (0.85±0.13 vs 0.99±0.05, p=0.032). The ratio of NAA/(Cho+Cr) in cerebellum after heat stroke was found to be statistically decreased compared to normal control subjects (0.42±0.06 vs 0.52±0.05, p=0.010). There had no statistical difference for the ratios of NAA/Cr2, Cho/Cr2, NAA/Cho (1.41±0.53比1.63±0.14, p=0.083; 1.58±0.52比1.58±0.17, p=0.908; 0.96±0.18比1.06±0.92, p=0.271) (p>0.05). The ratio of NAA/Cr in cerebellum after heat stroke was markedly correlated with the GCS score (r=0.748, p=0.033).Conclusion:Neural damage of cerebellum induced by heat stroke can be effectively evaluated by DTI and MRS. DTI and MRS play an important role in diagnosing and evaluating the prognosis of heat stroke.1. Neural damage of the cerebellum induced by HS may be effectively evaluated by DTI with the decrease of FA value in normal-appearing cerebellum structures.2. MRS is a very useful tool for evaluation of major changes in metabolite levels of the cerebellum after heat stroke. Heat stroke often lead to decreased NAA peak and may be accompanied by Lac peak.3. The severity of the illness can be judged through the ratio of NAA/Cr effectively. |
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