Significance of novel subcortical low intensity score on transient neurological events after revascularization surgery for moyamoya disease

The Dark side of the White Matter. Diffuse subcortical White Matter Hypointensity on T2/FLAIR: A systematic review of a frequently underrecognized sign

BACKGROUND AND OBJECTIVES

Many reversible brain MRI abnormalities have been described, among these the most frequently reported are cortical hyperintensities on FLAIR/T2 occurring during seizures. Much less attention has been given to those situations where White Matter goes Dark: subcortical white matter hypointensity on T2/FLAIR. Our aim is to identify the medical condition "Dark White Matter" (DWM) is more frequently associated with. This is the first systematic review on DWM.

METHODS

PubMed was searched in August 2023. Included studies were those reporting Diffuse Subcortical White Matter Hypointensity on T2/FLAIR. Mainly case reports were included. Individual patient-level data was included whenever available. Frequency measures of the different diseases were calculated.

RESULTS

56 studies were included, 228 patients were eligible for analysis. DWM happened in isolation, with no cortical abnormalities, in 71 cases and was associated with seizures in >61.4% of cases. The most frequently DWM-associated disease was Non-Ketotic Hyperglycaemic hyperosmolar state (NKH), followed by Encephalitis, Moyamoya disease, Genetic Causes, and Subdural Hematoma. Frequency of NKH was 32%. NKH was associated with seizures in 100% of cases and the most frequently involved lobe was the occipital one. When considering only the subgroup of patients with seizures, DWM was indicative of NKH in 51.4% of cases and Encephalitis in 26.4% of cases. Key limitations are heterogeneity and missing data.

DISCUSSION

DWM is frequently underdiagnosed. This sign can exist alone and it is not merely a consequence of cortical involvement. Moreover, it has important implications, both diagnostic and therapeutic, as it is more frequently associated with NKH, especially in the context of seizures, where anti-seizure medication is not the first line of treatment. We also discuss the pathogenesis of DWM by finding a common link between the most frequently associated diseases.

Transient neurological events in childhood moyamoya disease

OBJECTIVE

Patients sometimes experience transient neurological events (TNEs) during the early postoperative period after revascularization surgery for childhood moyamoya disease. The clinical background and pathophysiology of TNEs remain unclear. This study aimed to evaluate the incidence rate of TNEs and discuss the factors associated with pediatric moyamoya disease.

METHODS

The authors retrospectively reviewed 110 cerebral hemispheres of 61 pediatric patients younger than 15 years who were treated from 2011 to 2020. All children underwent either simple double-direct or combined revascularization surgery. Of these 61 patients, 52 underwent bilateral surgery and 9 underwent unilateral surgery. The authors calculated the incidence of TNEs in accordance with a previously reported TNE definition. Cerebral blood flow (CBF) was evaluated in all eligible cases with xenon CT immediately after revascularization surgery.

RESULTS

The incidence rate of TNEs in patients with childhood moyamoya disease was 26.4%. TNEs occurred after an average (range) of 6.26 (2-12) days postoperatively without triggers, and all identified TNEs spontaneously resolved within 2 weeks. The most common symptoms were dysarthria, facial palsy, and numbness around the mouth, followed by sensory disturbance of the upper extremities. The presence of focal hyperperfusion on xenon CT performed immediately after revascularization surgery was strongly correlated with the incidence of TNEs (p = 0.0001). Focal hyperperfusion was observed in 43 of 110 operative sides (39.1%). Notably, only 25.6% of patients with focal hyperperfusion showed numerical global hyperperfusion. In addition, a decrease in CBF compared with the thalamic region in the contralateral side was observed in TNE-affected cases (p = 0.0443).

CONCLUSIONS

TNEs occurred more frequently in childhood moyamoya disease patients than expected. The clinical background, including symptoms, timing, and duration, was almost identical to TNEs in adults. Focal hyperperfusion, rather than numerical global hyperperfusion, was strongly correlated with the incidence of TNEs. Furthermore, the authors advocate the notion that a clinical course where symptoms occur without triggers may be a unique characteristic of TNEs, especially in childhood moyamoya disease.

Endoscopically Treated Subacute Subdural Hematoma Presenting Postoperative Cerebral Hyperperfusion Syndrome: Chronological Changes of Cerebral Blood Flow on Arterial Spin Labeling and Subcortical Low Intensity on Fluid-attenuated Inversion Recovery Images

Subacute subdural hematoma (SASDH) is a neurotraumatic entity. There are few reports of chronological changes of cerebral blood flow (CBF) on arterial spin labeling (ASL) and subcortical low intensity (SCLI) on fluid-attenuated inversion recovery (FLAIR) images of magnetic resonance imaging (MRI) observations from the injury onset, deterioration, to post-surgery. We reported a SASDH patient presenting postoperative cerebral hyperperfusion (CHP) syndrome with chronological changes of those findings. An 85-year-old woman fell and presented right ASDH. She was treated conservatively due to no neurological deficits. On day 3, ASL image revealed increased CBF against brain compression. On day 7, the CBF was normalized on ASL image, but SCLI was confirmed. On day 14, SCLI was strengthened. Then she developed left hemiparesis due to brain compression by SASDH. Considering age and comorbidities, we performed endoscopic hematoma removal under local anesthesia, and her neurological deficits improved after the surgery. On postoperative day 1, she newly presented left upper limb paresis. MRI revealed increased CBF and enhanced SCLI. We diagnosed CHP syndrome, and antihypertensive treatment improved the symptoms gradually. However, SCLI had been consistently observed, and CBF easily changed depending on the blood pressure, suggesting dysfunction of the CBF autoregulation. We showed the endoscopically treated SASDH patient with CBF’s chronological changes on ASL images and SCLI on FLAIR images. Long-time brain compression would lead to dysfunction of the CBF autoregulation, and we should be careful about CHP syndrome after the endoscopic surgery for SASDH.

Predictors and clinical features of transient neurological events after combined bypass revascularization for moyamoya disease

OBJECTIVE

Transient neurological events (TNEs) are frequently observed after revascularization surgery for moyamoya disease (MMD). However, clinical features and pathophysiology of TNEs in MMD are still unclear. This study was aimed to clarify the incidence and time course of TNEs and to determine the independent predictors of TNEs in MMD.

PATIENTS AND METHODS

A total of 195 hemispheres in 171 consecutive patients with MMD who had undergone combined direct and indirect bypass surgery were analyzed. Preoperative clinical characteristics and radiographic features were recorded. The incidence and clinical feature of postoperative TNEs were evaluated. Multivariate logistic regression analyses were performed to identify the risk factors for postoperative TNEs. Outcomes were compared between patients who had TNEs with those without TNEs at the time of discharge.

RESULTS

Postoperative TNEs were detected in 40 (20.5%) of 195 operated hemispheres, including 17 (42.5%) aphasia, 9 numbness of the extremities (22.5%), 6 seizures (15%), 5 motor weakness (12.5%), 4 dysarthria (10%) and 6 others (15%). The incidence of TNEs was significantly higher in adult patients than in pediatric ones. Multivariate analysis revealed that female, left-sided surgery and the presence of the edematous lesion was an independent predictor of TNEs after surgery in MMD (OR, 3.0; 95% CI, 1.1-8.2; P = 0.03, OR, 2.9; 95% CI, 1.2-7.0; P = 0.02 and OR, 17.4; 95% CI, 5.7-53.0; P < 0.01, respectively). DSA stage (OR 0.05, 95% CI 0.0-0.5, p = 0.005; OR 0.08, 95% CI 0.0-0.4, p = 0.008), PCA involvement (OR 2.75, 95% CI 1.0-7.4, p = 0.046), left-sided surgery (OR 2.73, 95% CI 1.2-6.5, p = 0.022) and edematous lesion (OR 21.2, 95% CI 7.6-59.7, <0.001) were significantly associated with TNE severity. Compared with patients without postoperative TNEs, no significant differences in mRS score between the two groups were detected.

CONCLUSIONS

Female, left-sided surgery and edematous lesion were independent risk factors for postoperative TNEs; the left-sided surgery and edematous lesion were also independently associated with the severity of TNE. Although patients with postoperative TNEs had worse neurological status during the perioperative period, postoperative TNEs had no associations with worse mRS score at the time of discharge.

Cerebral Hyperperfusion Syndrome After a Burr Hole Drainage Surgery for Chronic Subdural Hematoma

BACKGROUND

Although chronic subdural hematoma (CSDH) has a good prognosis after classical minimally-invasive drainage surgery, severe complications still occur at a substantial rate. Cerebral hyperperfusion syndrome (CHS), which is a common severe complication after carotid endarterectomy or carotid artery stenting for cervical carotid artery stenosis, is rare after drainage surgery for a CSDH.

CASE DESCRIPTION

We describe the case of an 82-year-old woman who presented with ipsilesional symptoms including contralateral hemiparesis and dysarthria, progressively worsening consciousness, and status epilepticus after a burr hole drainage surgery for CSDH. Magnetic resonance fluid-attenuated inversion recovery imaging showed diffuse subcortical low intensity in the ipsilesional hemisphere almost simultaneously with the appearance of the symptoms. Arterial spin labeling magnetic resonance perfusion imaging showed the abnormal increase of cerebral blood flow in the hemisphere. Continuous propofol administration and blood pressure management improved the symptoms.

CONCLUSIONS

CHS can cause severe postoperative complications after drainage surgery for CSDH. Subcortical low-intensity fluid-attenuated inversion recovery imaging is a useful investigation for early detection of CHS in CSDH, and arterial spin labeling imaging is an effective minimally-invasive modality for confirming the diagnosis.