Extensive Microhemorrhages of the Cerebellar Peduncles After High-Altitude Cerebral Edema

Altitude illnesses

Millions of people visit high-altitude regions annually and more than 80 million live permanently above 2,500 m. Acute high-altitude exposure can trigger high-altitude illnesses (HAIs), including acute mountain sickness (AMS), high-altitude cerebral oedema (HACE) and high-altitude pulmonary oedema (HAPE). Chronic mountain sickness (CMS) can affect high-altitude resident populations worldwide. The prevalence of acute HAIs varies according to acclimatization status, rate of ascent and individual susceptibility. AMS, characterized by headache, nausea, dizziness and fatigue, is usually benign and self-limiting, and has been linked to hypoxia-induced cerebral blood volume increases, inflammation and related trigeminovascular system activation. Disruption of the blood-brain barrier leads to HACE, characterized by altered mental status and ataxia, and increased pulmonary capillary pressure, and related stress failure induces HAPE, characterized by dyspnoea, cough and exercise intolerance. Both conditions are progressive and life-threatening, requiring immediate medical intervention. Treatment includes supplemental oxygen and descent with appropriate pharmacological therapy. Preventive measures include slow ascent, pre-acclimatization and, in some instances, medications. CMS is characterized by excessive erythrocytosis and related clinical symptoms. In severe CMS, temporary or permanent relocation to low altitude is recommended. Future research should focus on more objective diagnostic tools to enable prompt treatment, improved identification of individual susceptibilities and effective acclimatization and prevention options.

Neuroimaging Features of High-Altitude Cerebral Edema: A Case Report

High-altitude cerebral edema (HACE) is serious, sometimes fatal clinical condition visualized in unacclimatized individuals climbing high altitudes. The current case report highlights a 39 year old male with a recent history of high-altitude mountain climbing and presented with memory impairment. The radiological findings revealed edema and microhemorrhages at genu and splenium of corpus callosum. Two months later the subject displayed complete resolution of edema, with persistent microhemorrhages. Herein, we report the radiological features of this rare clinical event. The lack of advanced imaging centers at higher altitudes elicit this clinical condition as less described entity.

High-altitude cerebral edema manifesting as T2/FLAIR hyperintensity and microbleeds in the white matter on MRI brain

High-altitude cerebral edema is a rare type of acute mountain illness characterized by consciousness disruption and truncal ataxia. Here we discuss a 40-year-old nondiabetic, nonsmoker male who went on a tour to Nanga Parbat. On returning home, the patient developed symptoms of headache, nausea, and vomiting. His symptoms worsened with time and he developed lower limb weakness and shortness of breath. Later, he underwent a computerized tomography chest scan. On the basis of CT scan findings, the doctors decided that the patient was suffering from COVID-19 Pneumonia despite having negative COVID-19 PCR tests multiple times. Later, the patient presented to our hospital with similar complaints. MRI of the brain revealed T2/fluid-attenuated inversion recovery hyperintense and T1 hypointense signals in the bilateral semioval centrum, posterior periventricular white matter, and corpus callosum genu, body, and splenium. These abnormal signals were discovered to be more evident in the corpus callosum's splenium. Moreover, susceptibility-weighted imaging revealed micro hemorrhages in the corpus callosum. This verified the diagnosis that the patient is suffering from high-altitude cerebral edema. Within 5 days, his symptoms resolved and he was discharged with full recovery.

Study of high-altitude cerebral edema using multimodal imaging

Objective

To analyze the brain imaging features of high-altitude cerebral edema (HACE) using computed tomography (CT) and multi-sequence magnetic resonance imaging (MRI) and to explore its injury characteristics.

Materials and methods

We selected 30 patients with HACE diagnosed between January 2012 to August 2022 as the experimental group and 60 patients with dizziness on traveling from the plain to the plateau or from lower altitude to higher altitude in a short period of time as the control group. We collected general clinical data from the experimental group and classified it according to clinical symptoms. In both groups, we then performed a head CT and multi-sequence MRI (T1WI, T2WI, FLAIR, and DWI). Among them, nine patients with HACE were also scanned using susceptibility-weighted imaging (SWI). Finally, we analyzed the images.

Results

According to clinical symptoms, we divided the 30 cases of HACE into 12 mild cases and 18 severe cases. There was no significant difference in sex, age, leukocyte, neutrophil, or glucose content between mild and severe HACE. The sensitivity and specificity of the MRI diagnosis were 100 and 100%, respectively, while the sensitivity and specificity of the CT diagnosis were 23.3 and 100%, respectively. The distribution range of deep and juxtacortical white matter edema was significantly larger in severe HACE than in mild HACE (p < 0.001). The corpus callosum edema distribution range in severe HACE was significantly larger than that in mild HACE (p = 0.001). The ADC value of the splenium of the corpus callosum was significantly lower in severe HACE than in mild HACE (p = 0.049). In mild and severe HACE, the signal intensity of the DWI sequence was significantly higher than that of conventional MRI sequences (T1WI, T2WI, FLAIR) (p = 0.008, p = 0.025, respectively). In severe HACE, seven cases showed bilateral corticospinal tract edema at the thalamic level, and SWI showed cerebral microbleeds (CMBs) in five cases, especially in the corpus callosum.

Conclusions

MRI has more advantages than CT in the evaluation of HACE, especially in the DWI sequence. The white matter injury of severe HACE is more severe and extensive, especially in the corpus callosum, and some CMBs and corticospinal tract edema may also appear.

High-altitude illnesses: Old stories and new insights into the pathophysiology, treatment and prevention

Areas at high-altitude, annually attract millions of tourists, skiers, trekkers, and climbers. If not adequately prepared and not considering certain ascent rules, a considerable proportion of those people will suffer from acute mountain sickness (AMS) or even from life-threatening high-altitude cerebral (HACE) or/and pulmonary edema (HAPE). Reduced inspired oxygen partial pressure with gain in altitude and consequently reduced oxygen availability is primarily responsible for getting sick in this setting. Appropriate acclimatization by slowly raising the hypoxic stimulus (e.g., slow ascent to high altitude) and/or repeated exposures to altitude or artificial, normobaric hypoxia will largely prevent those illnesses. Understanding physiological mechanisms of acclimatization and pathophysiological mechanisms of high-altitude diseases, knowledge of symptoms and signs, treatment and prevention strategies will largely contribute to the risk reduction and increased safety, success and enjoyment at high altitude. Thus, this review is intended to provide a sound basis for both physicians counseling high-altitude visitors and high-altitude visitors themselves.

Distinct pattern of microsusceptibility changes on brain magnetic resonance imaging (MRI) in critically ill patients on mechanical ventilation/oxygenation

Purpose

Over the years, interesting SWI abnormalities in patients from intensive care units (ICU) were observed, not attributable to a specific cause and with uncertain clinical significance. Recently, multiple SWI-hypointense foci were mentioned related to neurological complications of SARS-COV-2 infection. The purpose of the study was to describe the patterns of susceptibility brain changes in critically-ill patients who underwent mechanical ventilation and/or extracorporeal membrane oxygenation (ECMO).

Methods

An institutional board-approved, retrospective study was conducted on 250 ICU patients in whom brain MRI was performed between January 2011 and May 2020. Out of 48 patients who underwent mechanical ventilation/ECMO, in fifteen patients (median age 47.7 years), the presence of SWI abnormalities was observed and described.

Results

Microsusceptibilities were located in white-gray matter interface, in subcortical white matter (U-fibers), and surrounding subcortical nuclei in 13/14 (92,8%) patients. In 8/14 (57,1%) patients, SWI foci were seen infratentorially. The corpus callosum was affected in ten (71,4%), internal capsule in five (35,7%), and midbrain/pons in six (42,8%) patients.

Conclusion

We showed distinct patterns of diffuse brain SWI susceptibilities in critically-ill patients who underwent mechanical ventilation/ECMO. The etiology of these foci remains uncertain, but the association with mechanical ventilation, prolonged respiratory failure, and hypoxemia seems probable explanations.

Mountain sickness with delayed signal changes in the corpus callosum on magnetic resonance imaging: a case report

A 32-year-old man started building a wooden desk atop Mount Fuji at an altitude of 3,776 m. Over the course of the second day, he developed lassitude and cough and experienced a headache that night; however, he continued to work. He was transported to our hospital with an altered level of consciousness. On arrival, chest radiography revealed increased opacities in both lungs, and magnetic resonance imaging (MRI) revealed a high-intensity signal in the splenium on diffusion-weighted imaging. He received mechanical ventilation following tracheal intubation. His respiratory function improved, and he was extubated on the fourth hospital day. Physical examination showed no motor weakness, and although he responded to verbal commands, he was unable to speak and was unresponsive to visual stimulation. On the seventh hospital day, head MRI showed improvement in the lesion in the splenium, although other signal changes were observed in the body of the corpus callosum. His verbal responsiveness and voice volume improved on a daily basis. Two months after the incident, he continued to experience mild recent memory disturbance. The patient described in this case report showed delayed signal changes in the body of the corpus callosum, possibly secondary to the onset of microbleed-induced edema.

Neuroimaging features of fatal high-altitude cerebral edema

Acute high-altitude cerebral edema can occur in an unacclimatised individual on exposure to high altitudes and sometimes it can be fatal. Here we have described the neuroimaging features of a patient who suffered from fatal high altitude cerebral edema. Available literature is reviewed. Probable pathogenesis is discussed. The risk of acute mountain sickness is reported up to 25% in individuals who ascend to an altitude of 3500 meter and in more than 50% subjects at an altitude of 6000 meter. The lack of availability of advanced imaging facilities at such a higher altitude makes imaging of such condition a less described entity.