Delayed post-hypoxic leukoencephalopathy: case report with a review of disease pathophysiology

Case report: Consecutive hyperbaric oxygen therapy for delayed post-hypoxic leukoencephalopathy resulting from CHANTER syndrome caused by opioid intoxication

Delayed post-hypoxic leukoencephalopathy (DPHL) is a poorly recognized syndrome characterized by neuropsychiatric symptoms following recovery from an acute hypoxic episode. Although most cases are related to carbon monoxide poisoning, some have been linked to excessive opioid use. Opioid intoxication has recently become known for manifesting the characteristic imaging findings involving cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome. Herein, we present a patient with severe disturbances in consciousness who was initially diagnosed with CO poisoning but was later found to have taken excessive tramadol. Magnetic resonance imaging (MRI) in the acute phase revealed abnormal intensities in the bilateral globus pallidus and the cerebellum, indicative of CHANTER syndrome. After intensive care, his level of consciousness was restored. However, around the 3rd week after hospitalization, his consciousness gradually deteriorated and he developed severe neurological symptoms. Another MRI on day 25 revealed a new diffuse white matter abnormality; DPHL was suspected. Cerebrospinal fluid collected on day 28 revealed significantly elevated myelin basic protein levels. Although it was challenging to decide on a treatment plan, hyperbaric oxygen (HBO) therapy trials were initiated on day 58; the patient's condition improved after a series of HBO sessions. MRI revealed gradual shrinkage of the white matter abnormality. A total of 63 consecutive HBO sessions were performed, leading to the successful resolution of the serious neurological symptoms. While the effectiveness of HBO therapy for DPHL remains inconclusive, especially in opioid-related cases, this patient made a remarkable recovery, likely due to the therapeutic effect of improved cerebral blood flow and oxygenation.

Gray matter atrophy and white matter lesions burden in delayed cognitive decline following carbon monoxide poisoning

Gray matter (GM) atrophy and white matter (WM) lesions may contribute to cognitive decline in patients with delayed neurological sequelae (DNS) after carbon monoxide (CO) poisoning. However, there is currently a lack of evidence supporting this relationship. This study aimed to investigate the volume of GM, cortical thickness, and burden of WM lesions in 33 DNS patients with dementia, 24 DNS patients with mild cognitive impairment, and 51 healthy controls. Various methods, including voxel-based, deformation-based, surface-based, and atlas-based analyses, were used to examine GM structures. Furthermore, we explored the connection between GM volume changes, WM lesions burden, and cognitive decline. Compared to the healthy controls, both patient groups exhibited widespread GM atrophy in the cerebral cortices (for volume and cortical thickness), subcortical nuclei (for volume), and cerebellum (for volume) (p < .05 corrected for false discovery rate [FDR]). The total volume of GM atrophy in 31 subregions, which included the default mode network (DMN), visual network (VN), and cerebellar network (CN) (p < .05, FDR-corrected), independently contributed to the severity of cognitive impairment (p < .05). Additionally, WM lesions impacted cognitive decline through both direct and indirect effects, with the latter mediated by volume reduction in 16 subregions of cognitive networks (p < .05). These preliminary findings suggested that both GM atrophy and WM lesions were involved in cognitive decline in DNS patients following CO poisoning. Moreover, the reduction in the volume of DMN, VN, and posterior CN nodes mediated the WM lesions-induced cognitive decline.

A case report of long-term effects of Delayed post-hypoxic leukoencephalopathy (DPHL) following benzodiazepine overdose

Objective: We report a neuropsychological evaluation for a 39-year-old, right-handed, white female who 8 years ago developed delayed post-hypoxic leukoencephalopathy (DPHL), a rare demyelinating syndrome, two-weeks following an anoxic brain injury due to an overdose from benzodiazepines. Methods: An extensive record review documenting her medical timeline and treatment over the last 8 years was conducted using the available EMR system, which also included both EEG and neuroimaging data. Eight years post injury, a comprehensive neuropsychological battery was administered with corrected normative data for age, race, education, and other demographic factors when available. Collected data was compared with other case reports of DPHL. Results: The neuropsychological profile indicated difficulties across multiple cognitive domains that appeared driven by executive dysfunction, likely related to fronto-subcorto-striatal dysfunction. Conclusion: As a rare disease, the process by which DPHL occurs is not fully understood. Our results revealed similar findings in the literature for learning and memory, attention, processing speed, and executive functions. This is discussed in the context of available neuroimaging while highlighting the value of comprehensive neuropsychological assessment in DPHL even years post-injury.

Akinetic mutism and gait disturbance in a patient with delayed post-hypoxic leukoencephalopathy

We report on a patient with delayed post-hypoxic leukoencephalopathy (DPHL) who showed akinetic mutism and gait disturbance, neural injuries that were demonstrated on diffusion tensor tractography (DTT). A patient was exposed to carbon monoxide (CO) and rapidly recovered; however, two weeks after onset, he began to show cognitive impairment and gait disturbance. At six weeks after CO exposure, he showed akinetic mutism and gait inability. DTT at 6-weeks post-exposure showed discontinuations in neural connectivities of the caudate nucleus to the medial prefrontal and orbitofrontal cortex in both hemispheres. In addition, the corticoreticulospinal tract revealed severe thinning in both hemispheres.

A neuropsychiatric case of delayed post-hypoxic leukoencephalopathy from opioid intoxication resulting in Anton-Babinski syndrome and quadriplegia

This is the case of a 26-year-old male who developed Anton Babinski syndrome (ABS), quadriplegia, and delayed post-hypoxic leukoencephalopathy (DPHL) after an opioid overdose. He exhibited cortical blindness, visual anosognosia, and confabulation upon awakening. Several days later, he experienced acute psychosis and agitation. T2-FSE MRI revealed extensive supratentorial leukoencephalopathy involving both cerebral hemispheres, extending to the posterior corpus callosum due to cerebral anoxia. This case report will discuss different types of encephalopathy from opioid abuse, ABS, visual anosognosia, and confabulation's pathogenic mechanisms. It underscores the necessity of researching substance-induced neuropsychiatric disorders and their pathogenic mechanisms for effective treatments.

Toxic leukoencephalopathy versus delayed post-hypoxic leukoencephalopathy after oral morphine sulphate overdose

Toxic leukoencephalopathy (TLE) is a rare pathology caused by various substances including opioids (notably heroin), immunosuppressants, chemotherapy agents, cocaine, alcohol and carbon monoxide. However, although heroin is metabolised by the body into morphine, there is a striking paucity in cases of primary oral morphine-induced TLE, especially in the adult population. We present the case of a man in his 40s admitted to hospital in respiratory depression with a Glasgow Coma Scale (GCS) score of 6 after taking an overdose of oral morphine sulphate. Following a complete recovery to baseline, he was then readmitted with an acute deterioration in his neurobehavioural condition. Initial investigations returned normal but MRI showed changes characteristic for TLE.In cases of opioid toxicity such as ours, TLE is difficult to differentiate from delayed post-hypoxic leukoencephalopathy, due to their similar clinical presentation, disease progression and radiological manifestation. We explore how clinicians can approach this diagnostic uncertainty.

Cortical Blindness As A Sign of Delayed Post-Hypoxic Encephalopathy: A Case Report

We present a case of a 67-year-old female patient, who presented with acute cortical blindness five days after a successful resuscitation from cardiac arrest. The magnetic resonance tomography revealed a mild FLAIR signal increase of the bilateral occipital cortex. A lumbar puncture revealed considerably elevated tau protein levels, in the presence of normal phospho-tau, as a marker of brain injury, whilst neuron-specific enolase levels were normal. The diagnosis of delayed post-hypoxic encephalopathy was set. We hereby describe a rare clinical manifestation after initially successful resuscitation and encourage the studying of tau protein as a potential marker of this disease entity.

COVID-Related Leukoencephalopathy: Unusual MRI Features and Comparability to Delayed Post Hypoxic Ischemic Encephalopathy

COVID-19 related leukoencephalopathy can be multifactorial given the systemic effects of the viral disease. We present couple of cases with typical clinico-imaging stigmata of COVID-19 resulting in severe respiratory insufficiency. MR brain imaging revealed confluent diffuse supratentorial white matter T2 hyperintensity with restricted diffusion during the sub-acute course of the disease. The MR imaging pattern of leukoencephalopathy was non-specific but more comparable to delayed post-hypoxic leukoencephalopathy (DPHL) as also previously reported in COVID-19. Interestingly, T2 imaging showed unusual but peculiar finding of "accentuated medullary veins" in the superficial zones. No dural venous sinus thrombosis or micro-hemorrhages were present to explain "dots and stripes" due to dilated medullary veins. The patho-mechanism of this findings is not clear but may possibly be related to demyelination as DPHL has shown to be a demyelinating process. We present a review of COVID-related leukoencephalopathy with discussion on hypoxia-induced demyelinating process with accentuated medullary veins as possible associated marker.

Delayed Toxic-Hypoxic Leukoencephalopathy As Sequela of Opioid Overdose and Cerebral Hypoxia-Ischemia

Delayed leukoencephalopathy in the aftermath of toxic exposure and cerebral hypoxia-ischemia is known as “delayed post-hypoxic leukoencephalopathy” (DPHL) but the name “delayed toxic-hypoxic leukoencephalopathy” (DTHL) may be more accurate if toxic and hypoxic mechanisms are both involved in the pathogenesis of delayed leukoencephalopathy. DTHL is characterized by initial recovery from toxic exposure and cerebral hypoxia-ischemia, clinical stability over a few weeks, and subsequent neurological deterioration with the sudden emergence of diffuse white matter disease. A 46-year-old man suffered respiratory failure and hypotension as a result of opioid overdose. Brain MRI showed watershed infarcts and EEG showed diffuse theta-delta slowing consistent with global cerebral hypoperfusion. He recovered fully and was discharged with intact cognitive function. Three weeks later, he presented with abulia and psychomotor retardation. MRI revealed extensive white matter hyperintensity and EEG showed diffuse polymorphic delta activity. DTHL was diagnosed based on classic MRI features, history of opioid overdose and hypoxic brain injury, and negative test results for etiology of white matter disease. He developed akinetic mutism prompting administration of methylprednisolone 1000-mg IV q24h for five days. He also received amantadine 100-mg PO q12h. His cognition, motivation, and psychomotor function slowly improved and returned to baseline about two months after the overdose. Clinic reassessment two and a half months after the overdose revealed normal cognitive function, slight residual MRI hyperintensity, and mild EEG slowing anteriorly. Toxic-metabolic myelinopathy causing diffuse demyelination in the deep white matter is a perfect explanation for the patient’s neurological symptoms, MRI changes, EEG findings, and time course of recovery.

Neurocognitive impairments and brain abnormalities resulting from opioid-related overdoses: A systematic review

BACKGROUND

Non-fatal opioid-related overdoses have increased significantly over the past two decades and there have been increasing reports of brain injuries and/or neurocognitive impairments following overdose events. Limited preclinical research suggests that opioid overdoses may cause brain injury; however, little is known about such injuries in humans. The purpose this systematic review is to summarize existing studies on neurocognitive impairments and/or brain abnormalities associated with an opioid-related overdose in humans.

METHODS

PubMed, Web of Science, Ovid MEDLINE and PsyINFO were searched, without year restrictions, and identified 3099 articles. An additional 24 articles were identified by reviewing references. Articles were included if they were published in English, reported study findings in humans, included individuals 18 years of age or older, and reported an objective measure of neurocognitive impairments and/or brain abnormalities resulting from an opioid-related overdose. Six domains of bias (selection, performance, attrition, detection (two dimensions) and reporting were evaluated and themes were summarized.

RESULTS

Seventy-nine journal articles, published between 1973-2020, were included in the review. More than half of the articles were case reports (n = 44) and there were 11 cohort studies, 18 case series, and 6 case-control studies. All of the studies were categorized as at-risk of bias, few controlled for confounding factors, and methodological differences made direct comparisons difficult. Less than half of the studies reported toxicology results confirming an opioid-related overdose; 64.6 % reported brain MRI results and 27.8 % reported results of neuropsychological testing. Only two studies had within subject comparative data to document changes in the brain possibly associated with an overdose. Despite these limitations, existing publications suggest that brain injuries and neurocognitive impairments are associated with opioid overdose. Additional research is needed to establish the incidence of overdose-related brain injuries and the potential impact on functioning, as well as engagement in treatment of substance use disorders.

CONCLUSIONS

Respiratory depression is a defining characteristic of opioid overdose and prolonged cerebral hypoxia may cause brain injuries and/or neurocognitive impairments. The onset, characteristics, and duration of such injuries is variable and additional research is needed to understand their clinical implications.

Delayed post-hypoxic leukoencephalopathy following alcohol consumption and cardiopulmonary arrest

Delayed post hypoxic leukoencephalopathy (DPHL) is a rare consequence of hypoxic brain injury that occurs several days to weeks following an initial hypoxic insult. Most of the previously published cases occur in the setting of drug overdoses or carbon monoxide poisoning, where the incidence of DPHL is as high as 3%. Our case depicts a patient with delayed hypoxic brain injury following cardiac arrest with cardiopulmonary resuscitation. Initial neuroimaging was normal, and a repeat MRI scan six days later revealed DWI changes consistent with DPHL. Our patient remained comatose throughout his clinical course until his eventual death nine days after the initial incident. The autopsy confirmed hypoxic-ischemic brain injury with co-existent Wernicke's encephalopathy, a known consequence of alcohol use disorder. This case outlines the clinical course of DPHL accompanied by the unique neuroimaging features that distinguish it from conventional hypoxic-ischemic brain injury.

A case study of methadone-induced delayed post-hypoxic leukoencephalopathy with improvement by antioxidant therapy

Delayed post-hypoxic leukoencephalopathy (DPHL) is a syndrome that may occur as a result of the hypoxic event, including opiate overdose. The pathophysiology of this entity is not fully known. Within a neuropsychiatric context, the diagnosis of this rare disease is important. A 39-year-old man with a history of methadone overdose presented with loss of consciousness and fever. After clinical evaluations, laboratory analysis, including various tests on blood and cerebrospinal fluid and magnetic resonance imaging, the patient was diagnosed with methadone-induced DPHL. Treatment with antioxidants, including vitamins E, C and B complex, produced a favorable outcome. In rare cases, methadone overdose may lead to DPHL. Antioxidants therapy should be considered in the treatment of this rare disorder.

Clinical, Imaging, and Lab Correlates of Severe COVID-19 Leukoencephalopathy

BACKGROUND AND PURPOSE

Patients infected with the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) can develop a spectrum of neurological disorders, including a leukoencephalopathy of variable severity. Our aim was to characterize imaging, lab, and clinical correlates of severe coronavirus disease 2019 (COVID-19) leukoencephalopathy, which may provide insight into the SARS-CoV-2 pathophysiology.

MATERIALS AND METHODS

Twenty-seven consecutive patients positive for SARS-CoV-2 who had brain MR imaging following intensive care unit admission were included. Seven (7/27, 26%) developed an unusual pattern of "leukoencephalopathy with reduced diffusivity" on diffusion-weighted MR imaging. The remaining patients did not exhibit this pattern. Clinical and laboratory indices, as well as neuroimaging findings, were compared between groups.

RESULTS

The reduced-diffusivity group had a significantly higher body mass index (36 versus 28 kg/m², P < .01). Patients with reduced diffusivity trended toward more frequent acute renal failure (7/7, 100% versus 9/20, 45%; P = .06) and lower estimated glomerular filtration rate values (49 versus 85 mL/min; P = .06) at the time of MRI. Patients with reduced diffusivity also showed lesser mean values of the lowest hemoglobin levels (8.1 versus 10.2 g/dL, P < .05) and higher serum sodium levels (147 versus 139 mmol/L, P = .04) within 24 hours before MR imaging. The reduced-diffusivity group showed a striking and highly reproducible distribution of confluent, predominantly symmetric, supratentorial, and middle cerebellar peduncular white matter lesions (P < .001).

CONCLUSIONS

Our findings highlight notable correlations between severe COVID-19 leukoencephalopathy with reduced diffusivity and obesity, acute renal failure, mild hypernatremia, anemia, and an unusual brain MR imaging white matter lesion distribution pattern. Together, these observations may shed light on possible SARS-CoV-2 pathophysiologic mechanisms associated with leukoencephalopathy, including borderzone ischemic changes, electrolyte transport disturbances, and silent hypoxia in the setting of the known cytokine storm syndrome that accompanies severe COVID-19.

Storms and silence: a case report of catatonia and paroxysmal sympathetic hyperactivity following cerebral hypoxia

BACKGROUND

Delayed Post Hypoxic Leukoencephalopathy (DPHL) is a syndrome that occurs after hypoxia, and can present with a variety of neuropsychiatric symptoms, including catatonia and paroxysmal sympathetic hyperactivity (PSH). The gold standard for the treatment of catatonia is electroconvulsive therapy (ECT). However, ECT can exacerbate the paroxysms of sympathetic hyperactivity and complicate recovery from DPHL. The treatment of PSH is not well established.

CASE PRESENTATION

We present a case of a patient with multiple opiate overdoses who presented with altered mental status. He was diagnosed with catatonia and subsequently treated with ECT. His clinical condition worsened, and a revised diagnosis of PSH was established. The patient's condition improved with medical management.

CONCLUSION

This case highlights the need to distinguish between these two related symptom clusters, as the incidence of DPHL and opioid overdose related neuropsychiatric problems increase. This distinction can greatly influence the course of treatment, and the need to consider alternative treatments.

Methadone-induced encephalopathy: a case series and literature review

BACKGROUND

Accidental ingestion or consumption of supra-therapeutic doses of methadone can result in neurological sequelae in humans. We aimed to determine the neurological deficits of methadone-poisoned patients admitted to a referral poisoning hospital using brain magnetic resonance (MR) and diffusion weighted (DW) imaging.

METHODS

In this retrospective study, brain MRIs of the patients admitted to our referral center due to methadone intoxication were reviewed. Methadone intoxication was confirmed based on history, congruent clinical presentation, and confirmatory urine analysis. Each patient had an MRI with Echo planar T1, T2, FLAIR, and DWI and apparent deficient coefficient (ADC) sequences without contrast media. Abnormalities were recorded and categorized based on their anatomic location and sequence.

RESULTS

Ten patients with abnormal MRI findings were identified. Eight had acute- and two had delayed-onset encephalopathy. Imaging findings included bilateral confluent or patchy T2 and FLAIR high signal intensity in cerebral white matter, cerebellar involvement, and bilateral occipito-parietal cortex diffusion restriction in DWI. Internal capsule involvement was identified in two patients while abnormality in globus pallidus and head of caudate nuclei were reported in another. Bilateral cerebral symmetrical confluent white matter signal abnormality with sparing of subcortical U-fibers on T2 and FLAIR sequences were observed in both patients with delayed-onset encephalopathy.

CONCLUSIONS

Acute- and delayed-onset encephalopathies are two rare adverse events detected in methadone-intoxicated patients. Brain MRI findings can be helpful in detection of methadone-induced encephalopathy.

Acute loss of psychic self-activation after cardiac arrest and delayed bilateral pallidal lesions on brain MRI

The delay between cardiac arrest and brain MRI is usually extremely different in the few cerebral imaging studies assessing the affected brain areas. We report an unusual case of loss of psychic self-activation appeared immediately after a cardiac arrest in a middle age patient. The first brain MRI, one month after the vascular event, did not show the classical lesions typically reported, such as lesion of the caudate nucleus or the globus pallidus. Two years later, although the cognitive performances of our patient were improved, a second brain MRI demonstrated bilateral pallidal lesions, suggesting a possible mechanism with delayed hypoxic lesions.

Delay-Dependent Impairments in Memory and Motor Functions After Acute Methadone Overdose in Rats

Methadone is used as a substitution drug for the treatment of opioid dependence and chronic pain. Despite its widespread use and availability, there is a serious concern with respect to the relative safety of methadone. The purpose of this study was to characterize how acute methadone overdose affects the cognitive and motor performance of naïve healthy rats. The methadone overdose was induced by administering an acute toxic dose of methadone (15 mg/kg; ip; the equivalent dose of 80% of LD50) to adolescent rats. Resuscitation using a ventilator pump along with a single dose of naloxone (2 mg/kg; ip) was administered following the occurrence of apnea. The animals which were successfully resuscitated divided randomly into three apnea groups that evaluated either on day 1, 5, or 10 post-resuscitation (M/N-Day 1, M/N-Day 5, and M/N-Day 10 groups) in the Y-maze and novel object memory recognition tasks as well as pole and rotarod tests. The data revealed that a single toxic dose of methadone had an adverse effect on spontaneous behavior. In addition, Recognition memory impairment was observed in the M/N-Day 1, 5, and 10 groups after methadone-induced apnea. Further, descending time in the M/N-Day 5 group increased significantly in comparison with its respective Saline control group. The overall results indicate that acute methadone-overdose-induced apnea produced delay-dependent cognitive and motor impairment. We suggest that methadone poisoning should be considered as a possible cause of delayed neurological disorders, which might be transient, in some types of memory or motor performance in naïve healthy rats.

Delayed posthypoxic leukoencephalopathy following alcohol and psychotropic drug overdose: a case report

Delayed posthypoxic leukoencephalopathy (DPHL), a demyelinating syndrome, can easily be misdiagnosed as a psychiatric condition. Our case study shows that magnetic resonance imaging is highly useful for an early diagnosis of DPHL and that vascular endothelial growth factor might be a supplementary biomarker for the early detection of DPHL.

Delayed Post-hypoxic Leukoencephalopathy: A Case Series and Review of the Literature

Delayed post-hypoxic leukoencephalopathy (DPHL) is a unique clinical entity that presents with cognitive impairment days to weeks after an episode of acute hypoxic brain injury. Frequently hypoxia is unrecognized as a mechanism for clinical decline and extensive workup ensues. We present two cases of DPHL highlighting the neuroimaging findings. In both patients, a cerebral hypoxic event was followed by a recovery phase with subsequent delayed clinical decline. Patient 1 suffered hypoxia from drug-induced respiratory depression and lack of post-operative positive airway pressure (PAP) support. Her neurological exam on follow-up revealed progressive cognitive decline. Magnetic resonance imaging (MRI) brain showed bilateral white matter changes involving the centrum semiovale. Patient 2 developed a generalized tonic-clonic seizure during an endobronchial biopsy procedure and was found to have multiple air emboli on computed tomography (CT) head scan. She was initially in a drug-induced coma for her seizures. Electroencephalography (EEG) on day 14 of admission showed changes consistent with diffuse encephalopathy. MRI brain showed bilateral white matter changes particularly at the watershed zones and in the centrum semiovale. DPHL is a rare and under-recognized clinical entity that requires clinical suspicion and detailed evaluation for diagnosis. Neuroimaging studies can provide prognostic information regarding the extent of neurological injury.

Delayed-onset Reversible Cortical Blindness after Resuscitation from Cardiac Arrest

We present a patient who presented with cortical blindness (CB) 1 week after repeated cardiac arrest while undergoing treatment for an acute myocardial infarction. He had been revived within 5 min in each instance and was apparently neurologically normal until presentation. Magnetic resonance imaging showed subtle hyperintensities on fluid-attenuated inversion recovery and diffusion-weighted imaging in both temporooccipital cortices. A rapid recovery over the next 2 weeks was remarkable for the appearance of metamorphopsia. CB may present even days to weeks after hypoxic-ischemic encephalopathy following cardiac arrest, even in patients apparently without immediate neurological sequelae. The pathogenesis of this phenomenon remains to be fully elucidated, but is likely to be due to delayed effects of anoxia on the occipital cortex and may be analogous to the previously described syndrome of delayed posthypoxic leukoencephalopathy. Prognosis for visual recovery appears to be good.

Injury of ascending reticular activating system associated with delayed post-hypoxic leukoencephalopathy: a case report

Background

Delayed post-hypoxic leukoencephalopathy (DPHL) is a demyelinating syndrome characterized by neurological relapse after an initial recovery from hypoxic brain injury. We describe a patient with impaired consciousness following DPHL, concurrent with injury of the ascending reticular activating system (ARAS) shown using diffusion tensor tractography (DTT).

Case presentation

A 50-year-old male patient was in a drowsy mental state after exposure to carbon monoxide (CO) for about ten hours. About a day after the CO exposure, his mental state recovered to an alert condition. However, his consciousness deteriorated to drowsy 24 days after the exposure and worsened to a semi-coma state at 26 days after onset. When he started rehabilitation six weeks after the CO exposure, he had impaired consciousness, with a Glasgow Coma Scale score of 8 and a Coma Recovery Scale-Revised score of 8. On 6-week DTT, decreased neural connectivity of the upper ARAS between the intralaminar thalamic nucleus and the cerebral cortex was observed in both frontal cortices, basal forebrains, basal ganglia and thalami. The lower dorsal ARAS was not reconstructed on the right side, and was thin on the left side. The lower ventral ARAS was not reconstructed on either side.

Conclusions

Using DTT, we demonstrated injury of the ARAS in a patient with impaired consciousness following DPHL. Our result suggests that injury of the ARAS is a plausible pathogenetic mechanism of impaired consciousness in patients with DPHL.

Delayed posthypoxic leukoencephalopathy: a case series and review of the literature

BACKGROUND

Delayed posthypoxic leukoencephalopathy (DPHL) is a rare and underrecognized entity where patients manifest a neurological relapse after initial recovery from an acute hypoxic episode. We sought to describe the magnetic resonance imaging (MRI) findings in a group of patients with DPHL and review the available literature.

METHODS

Retrospective case series including patients who presented with neurological and/or psychiatric symptoms after recovery from an acute hypoxic episode. The history and clinical presentation were reviewed from the electronic medical records. MRI scans were evaluated from the picture archiving and communication system. We performed a comprehensive review of the English medical literature for prior published cases of DPHL and describe the key imaging findings that have been reported related to this condition.

RESULTS

A total of five patients were identified, including four patients with respiratory failure due to drug overdoses from benzodiazepines, opioids, and/or barbiturates, and one patient who presented after cardiopulmonary arrest due to pulmonary embolism. All patients showed diffuse, extensive, and confluent white matter signal abnormalities including prominent restricted diffusion, extending to the subcortical white matter and respecting the U-fibers. There was no gyral edema or contrast enhancement. In one case histopathology was available, which highlighted patchy subcortical myelin loss with sparing of U-fibers and demonstrated prominent macrophage/microglial inflammation with extensive axonal damage. Of the other four patients, two were at their neurological baselines and two had persistent neurological deficits at the time of discharge.

CONCLUSIONS

The described constellation of MRI findings is highly suggestive of DPHL in the appropriate clinical setting.