Neuroimaging Findings in CHANTER Syndrome: A Case Series

Unmasking CHANTER syndrome: A rare neurological consequence of opioid overdose

The opioid epidemic remains a major public health issue in the U.S., with over 100,000 overdose deaths in 2022, many linked to synthetic opioids. Emergency medicine plays a vital role in managing opioid overdoses, which typically cause CNS depression and respiratory failure. However, atypical presentations are becoming more common, complicating diagnosis and treatment. This case report discusses a patient who developed focal neurologic deficits after an opioid overdose and was found to have radiographic findings suggestive of CHANTER syndrome. Cerebellar-Hippocampal-Basal Nuclei Transient Edema with Restricted Diffusion (CHANTER syndrome), first described in 2019, is marked by restricted diffusion and edema in the cerebellum, hippocampus, and basal ganglia. While most cases involve comatose patients requiring intensive care, the emergency department presentation is less understood. The differential diagnosis includes hypoxic-ischemic encephalopathy, posterior reversible encephalopathy syndrome, and heroin-associated spongiform leukoencephalopathy. Unlike ischemic infarcts, CHANTER syndrome can show significant improvement with aggressive management. Given the rise of opioid use, emergency physicians are likely to encounter more cases with similar presentations. MRI imaging should be considered in patients who do not recover as expected following an opioid overdose. Early identification of complications like CHANTER syndrome can lead to closer neurologic monitoring and neurosurgical intervention that may prevent decompensation or even death.

Dextromethorphan-Associated Neurotoxicity with Cerebellar Edema Syndrome in Young Children: Neuroimaging Features

Dextromethorphan toxicity in young children (especially those 4 years of age or younger) can have an extremely poor prognosis if untreated. However, if timely recognized and optimally managed, it can have a good clinical outcome despite a profound initial insult. We present 3 pediatric cases (younger than 5 years of age) with sudden unresponsiveness following ingestion of cough medications containing dextromethorphan. All these children showed cytotoxic edema in the cerebellar hemispheres on MR of the brain, with diffusion-restricting foci in the supratentorial white matter in 2 patients. These features resemble the recently described acute opioid toxidrome in children, pediatric opioid use-associated neurotoxicity with cerebellar edema (POUNCE). Hence, we named this entity dextromethorphan-associated neurotoxicity with cerebellar edema (DANCE) to increase the awareness of dextromethorphan toxicity in young children and the need to promptly recognize it to initiate optimal management.

Radiographic Findings of Evolving Sequelae of Cerebellar, Hippocampal, and Basal Nuclei Transient Edema With Restricted Diffusion (CHANTER) Syndrome in a 37-Year-Old Patient

Cerebellar, Hippocampal, and Basal Nuclei Transient Edema with Restricted Diffusion (CHANTER) syndrome is a recently recognized distinct clinicoradiographic pattern of neurologic injury occurring most commonly following polysubstance or opioid abuse. Patients present acutely with unresponsiveness or coma. Magnetic resonance (MR) imaging demonstrates key findings, including bilateral diffusion restriction in the cerebellar cortices and hippocampi and variable diffusion restriction in the basal ganglia. Additionally, cerebellar cytotoxic edema can exert a mass effect on the adjacent fourth ventricle, causing obstructive hydrocephalus and requiring emergent intervention to prevent brain herniation and death. Here, we present a 37-year-old male patient who arrived at the Emergency Department with non-responsiveness in the setting of positive toxicology for cannabis, cocaine, and fentanyl. One day following the presentation, an MRI demonstrated restricted diffusion of the bilateral cerebellar hemispheres and bilateral hippocampi and small foci of restricted diffusion involving the basal ganglia. T2 fluid-attenuated inversion recovery (T2 FLAIR) hyperintensities involving the bilateral precentral gyri were also identified. Additional diagnostic workup, including electroencephalogram (EEG), vessel imaging, and viral panels, effectively ruled out alternative diagnoses, making CHANTER most likely. Following medical treatment without surgical intervention, the patient was discharged to an acute rehab facility with symptoms of impaired judgment, difficulty following commands, and difficulty walking. In the following months, the patient improved in cognitive function and gait. MRI at three months demonstrated interval resolution of previous T2 FLAIR hyperintensities, restricted diffusion zones, and development of new T2 FLAIR hyperintensities in the periventricular and subcortical white matter. This case highlights the need for prompt recognition of radiographic features of CHANTER, as affected patients may demonstrate significant recovery of neurologic status in the months following injury, compared to other patterns of hypoxic brain injury. These patients, therefore, merit more aggressive treatment to maximize recovery.

Histopathologic correlates of opioid-associated injury in CHANTER syndrome: first report of a post-mortem examination

Opioid-associated brain injury may involve selective regions, including the hippocampi alone, globi pallidi, and cerebellar hemispheres. Opioid-associated amnestic syndrome, for example, is one clinical correlate of hippocampal injury as manifest by MRI abnormality. When all three regions are involved in what may be a more fulminant injury, the syndrome is termed "cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER)", initially described in 2019. Until now, to our knowledge, there have been no histopathologic correlates to the imaging findings specifically in CHANTER syndrome. Here, for the first time, we present histopathologic findings of the post-mortem brain from a patient who died from complications of CHANTER syndrome following fentanyl intoxication. These observations included microhemorrhage, reactive and necrotic vasculature, eosinophilic neuronal necrosis, axonal swelling and spheroids, and frank infarction. The findings support previous experimental models implicating both hypoxic-ischemic and cytotoxic mechanisms in the tissue damage associated with CHANTER syndrome, though further work is needed to better characterize the exact cellular pathways involved to develop targeted treatments.

CHANTER syndrome in the context of pain medication: a case report

BACKGROUND

CHANTER (Cerebellar Hippocampal and Basal Nuclei Transient Edema with Restricted diffusion) is a recently described syndrome occurring in the context of drug abuse. While clinical findings are rather unspecific (disorientation, unresponsiveness), MR imaging (MRI) discloses a characteristic pattern (restricted diffusion in the basal ganglia and hippocampi, cerebellar oedema and haemorrhage), allowing for timely diagnosis before complications such as cerebellar swelling and herniation do occur. Here we report a case of CHANTER primarily based on imaging findings, as there was no evidence of drug abuse on admission.

CASE PRESENTATION

A 62-year-old Patient was admitted to our hospital after being unresponsive at home. Prehospital intubation was performed, which limited neurological assessment. Under these circumstances no obvious symptoms could be determined, i.e. pupils were isocoric and responsive, and there were no signs of seizures. While the initial CT scan was unremarkable, the subsequent MRI scan showed a distinct imaging pattern: moderately enhancing areas in the basal ganglia and hippocampi with diffusion restriction, accompanied by cerebellar haemorrhage and oedema (Figs. 1 and 2). A comprehensive clinical and laboratory work-up was performed, including drug screening, spinal tap, Holter ECG, echocardiography and EEG. The only conspicuous anamnestic finding was a chronic pain syndrome whose medication had been supplemented with opioids two months previously. The opioid medication was discontinued, which led to a rapid improvement in the patient's clinical condition without any further measures. The patient was able to leave the intensive care unit and was discharged 10 days after admission without persistent neurological deficits.

CONCLUSION

Familiarity with typical MRI patterns of toxic encephalopathy in patients from high-risk groups, such as drug abusers, is crucial in emergency neuroradiology. In the presence of typical MRI findings, CHANTER syndrome should be included in the differential diagnosis, even if there is no history of drug abuse, to avoid delay in diagnosis and treatment.

Case of pediatric cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome in a 2-year-old girl

Cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome is a recently described entity that refers to a specific pattern of cerebellar edema with restricted diffusion and crowding of the fourth ventricle among other findings. The syndrome is commonly associated with toxic opioid exposure. While most commonly seen in adults, we present a case of a 2-year-old girl who survived characteristic history and imaging findings of CHANTER syndrome.

Case 324: CHANTER Syndrome

HISTORY

A 69-year-old right-handed man with a history of substance use disorder, hypertension, and diabetes presented to the emergency department in an unresponsive state. Upon examination, apart from tachycardia (heart rate, 108 beats per minute), vital signs were within normal ranges (blood pressure, 134/102 mm Hg; temperature, 97.9 ºF (36.6 ºC); respiratory rate, 16 per minute; oxygen saturation, 96%). The patient had a Glasgow coma scale score of 8. Otherwise, the physical examination revealed no abnormalities. Prior psychiatric and surgical histories were unremarkable. There was no history of recent travel, camping, hiking, or vaccination. No family history could be obtained. Laboratory work-up revealed an elevated creatine kinase level (49 006 U/L [818.4 μkat/L]; normal reference range, 10-205 U/L [0.17-3.42 μkat/L]). An electrocardiogram showed sinus tachycardia without evidence of cardiac ischemia. An echocardiogram was unremarkable. Alanine aminotransferase (126 U/L [2.10 μkat/L]; normal reference range, 0-40 U/L [0-0.67 μkat/L]) and aspartate aminotransferase (488 U/L [8.15 μkat/L]; normal reference range, 3-44 U/L [0.05-0.74 μkat/L]) levels were elevated. Polymerase chain reaction results were negative for HIV-1, HIV-2, syphilis treponemal, and COVID-19 antibodies. The remaining routine laboratory work-up findings were within normal limits. Urine drug screening was positive for cocaine, marijuana, fentanyl, and benzodiazepines. Naloxone was administered, but the patient remained unresponsive. Intubation was performed for airway protection. Noncontrast and contrast-enhanced CT of the head and CT angiography were performed in the emergency department to rule out an acute intracranial abnormality. Multisequence MRI of the brain with administration of intravenous contrast material was ordered for further assessment. CT of the abdomen and pelvis was unremarkable (images not shown).

Cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome in the setting of opioid and phencyclidine use

Cerebellar, hippocampal, and basal nuclei transient edema with restricted diffusion (CHANTER) syndrome is a constellation of specific imaging findings characterized by cytotoxic edema in the bilateral hippocampi, cerebellar cortices, and basal ganglia in patients presenting with altered mental status in the setting of substance intoxication. Previous case reports have demonstrated a strong correlation between CHANTER syndrome and polysubstance abuse, particularly with opioid intoxication. The patient we present in this case was found unresponsive following opioid use and demonstrated a constellation of findings on initial and follow-up imaging, consistent with CHANTER syndrome. While cases of irreversible brain damage or death during hospitalization have been reported in the literature, our patient demonstrated near-full recovery a few days after admission to the hospital. We aim to highlight the presentation and progression of CHANTER syndrome and alert clinicians and radiologists to include this entity in their diagnostic checklist for patients with polysubstance abuse and altered mental status.