Usefulness of subtraction of 3D T2WI-DRIVE from contrast-enhanced 3D T1WI: preoperative evaluations of the neurovascular anatomy of patients with neurovascular compression syndrome

The Anterior Inferior Cerebral Artery Variability in the Context of Neurovascular Compression Syndromes: A Narrative Review

The anterior inferior cerebellar artery (AICA) is situated within the posterior cranial fossa and typically arises from the basilar artery, usually at the pontomedullary junction. AICA is implicated in various clinical conditions, encompassing the development of aneurysms, thrombus formation, and the manifestation of lateral pontine syndrome. Furthermore, owing to its close proximity to cranial nerves within the middle cerebellopontine angle, AICA's pulsatile compression at the root entry/exit zone of cranial nerves may give rise to specific neurovascular compression syndromes (NVCs), including hemifacial spasm (HFS) and geniculate neuralgia concurrent with HFS. In this narrative review, we undertake an examination of the influence of anatomical variations in AICA on the occurrence of NVCs. Significant methodological disparities between cadaveric and radiological studies (CTA, MRA, and DSA) were found, particularly in diagnosing AICA's absence, which was more common in radiological studies (up to 36.1%) compared to cadaver studies (less than 5%). Other observed variations included atypical origins from the vertebral artery and basilar-vertebral junction, as well as the AICA-and-PICA common trunk. Single cases of arterial triplication or fenestration have also been documented. Specifically, in relation to HFS, AICA variants that compress the facial nerve at its root entry/exit zone include parabola-shaped loops, dominant segments proximal to the REZ, and anchor-shaped bifurcations impacting the nerve's cisternal portion.

The Use of MRI in Preoperative Decision-Making for Trigeminal Neuralgia: A Single-Center Study

OBJECTIVE

Few studies have examined associations between vascular compression and postoperative pain relief in patients undergoing microvascular decompression (MVD) for treatment of medically refractory type 1 trigeminal neuralgia (TN). The authors sought to examine for associations between vascular compression and postoperative pain relief to determine the utility of preoperative magnetic resonance imaging (MRI) in surgical decision-making for TN.

METHODS

The charts of 59 patients who underwent 60 MVDs for TN between 2007 and 2017 at a single academic institution were reviewed. Patient demographics, the presence of compressing vessel on preoperative MRI and intraoperatively, complications, follow-up time, performance of a partial sensory rhizotomy, and pain resolution at most recent follow-up were recorded. Sensitivity and specificity of MRI for detecting vascular compression were calculated and associations between preoperative and intraoperative evidence of vascular compression with postoperative pain relief were examined.

RESULTS

Sensitivity and specificity of preoperative MRI determined through blinded reads by the senior author were 65.3% (95% confidence interval, 13.5-32.0) and 90.9% (95% confidence interval, 86.1-100.0), respectively. Overall, 76.3% of patients were pain free at most recent follow-up. Preoperative MRI and intraoperative evidence of vascular compression were not associated with postoperative pain relief at most recent follow-up (P = 0.47 and 0.43, respectively).

CONCLUSIONS

The findings of lower sensitivity and poor interrater reliability of MRI, as well as a lack of association between compressive vessel and postoperative pain relief reported in this study, suggest the decision to pursue MVD for TN should be based more heavily on classic symptomatic presentation over preoperative evidence of vascular compression.

A preliminary study of deep learning-based reconstruction specialized for denoising in high-frequency domain: usefulness in high-resolution three-dimensional magnetic resonance cisternography of the cerebellopontine angle

PURPOSE

Deep learning-based reconstruction (DLR) has been developed to reduce image noise and increase the signal-to-noise ratio (SNR). We aimed to evaluate the efficacy of DLR for high spatial resolution (HR)-MR cisternography.

METHODS

This retrospective study included 35 patients who underwent HR-MR cisternography. The images were reconstructed with or without DLR. The SNRs of the CSF and pons, contrast of the CSF and pons, and sharpness of the normal-side trigeminal nerve using full width at half maximum (FWHM) were compared between the two image types. Noise quality, sharpness, artifacts, and overall image quality of these two types of images were qualitatively scored.

RESULTS

The SNRs of the CSF and pons were significantly higher with DLR than without DLR (CSF 21.81 ± 7.60 vs. 15.33 ± 4.03, p < 0.001; pons 5.96 ± 1.38 vs. 3.99 ± 0.48, p < 0.001). There were no significant differences in the contrast of the CSF and pons (p = 0.225) and sharpness of the normal-side trigeminal nerve using FWHM (p = 0.185) without and with DLR, respectively. Noise quality and the overall image quality were significantly higher with DLR than without DLR (noise quality 3.95 ± 0.19 vs. 2.53 ± 0.44, p < 0.001; overall image quality 3.97 ± 0.17 vs. 2.97 ± 0.12, p < 0.001). There were no significant differences in sharpness (p = 0.371) and artifacts (p = 1) without and with DLR.

CONCLUSION

DLR can improve the image quality of HR-MR cisternography by reducing image noise without sacrificing contrast or sharpness.

A segmentation-independent volume rendering visualisation method might reduce redundant explorations and post-surgical complications of microvascular decompression

OBJECTIVES

This study aimed to investigate the feasibility of segmentation-independent volume rendering (SI-VR) in visualising the root entry zone (REZ), and to explore the influence on the management of vascular compression syndromes (VCSs).

METHODS

Two hundred and twenty patients with VCSs were recruited in this prospective study from July 2015 to May 2019. SI-VR was reconstructed based on inverted 3D fast spin echo T2WI. They were assigned to the experimental group and control group randomly. Patients in the experimental group would accept extra evaluation based on SI-VR before microvascular decompression. Image quality and diagnostic accuracy between SI-VR and 3D fast spin echo T2WI in the experimental group were compared by Mann-Whitney U test and chi-square test, separately. Interobserver agreement was performed with intraclass correlation coefficient. Postsurgical outcomes and complications between two groups were compared by chi-square test.

RESULTS

SI-VR had a better interobserver agreement (0.82 vs 0.68) and diagnostic accuracy (95.5% vs 83.6%, p = 0.004) than that of 3D fast spin echo T2WI. Especially, significantly improved diagnostic accuracy was reached in detecting the multi-vascular branches compression (100% vs 15.4%, p < 0.001). There were fewer complications (7.1% vs 26.8%, p = 0.004) and less operation time (20.7 min vs 14.5 min, p = 0.007) but no significant difference of pain relief (p = 0.19) in the experimental group than in the control group.

CONCLUSIONS

The SI-VR method is feasible for the precise demonstration of the anatomy structure along the REZ, with high reliability and reproducibility. Unbiased pre-surgical visualisation could reduce redundant explorations and post-surgical complications in patients who undergo microvascular decompression.

KEY POINTS

• Visualisation of the root entry zone by the segmentation-independent volume rendering is in accordance with the landscape by the neuro-endoscopy. • Segmentation-independent volume rendering has an advantage over 3D fast spin echo T2WI in the visualisation of multi-vascular branches compression. • Presurgical 3D visualisation of the neurovascular compression at the root entry zone leads to less postsurgical complications from the decrease of redundant exploration.

Acute presentations of intradural lipomas: case reports and a review of the literature

BACKGROUND

Lumbosacral lipomas (LLs) may remain asymptomatic or lead to progressive neurological deterioration. However, sudden neurological deterioration is a rare and severe event. Herein, we report rare occurrences of sudden clinical deterioration in two previously asymptomatic children harbouring intradural LLs without dermal sinus tracts or signs of occult dysraphism. A review of the pertinent literature is also included.

CASE PRESENTATION

One child exhibited acute deterioration because of an epidural abscess associated with a filar lipoma without a sinus tract (probably caused by haematogenous spreading from a respiratory tract multiple infection), and the other child exhibited acute deterioration because of a very large, holocord syringomyelia-like cyst associated with a small conus lipoma. Both patients were 4 years old. In case #2, a previously undetected, severe tethered cord (conus at the S3-S4 level) was also present. A complete recovery was attained after an urgent surgical operation in both cases (in addition to targeted antibiotic therapy in case #1). All cases of deterioration in the literature were caused by abscess formation in dermal sinus tracts.

CONCLUSIONS

Prophylactic surgery may be indicated even in asymptomatic children that have tethered cord and surgically favourable LLs (small dorsal and filar LLs), especially if the conditions are associated with progressive syringomyelia. Similarly, intradural dermal sinus tracts should be regarded as surgery-indicated, even if the conus is in its normal position and the patient is asymptomatic because there is a consistent risk of severe, infection-related complications. Finally, asymptomatic patients with filar LLs and a normally located conus can be candidates for surgery or an accurate clinical and radiological follow-up.

Reliability of MRI for predicting characteristics of neurovascular conflicts in trigeminal neuralgia: implications for surgical decision making

OBJECTIVE

The choice of microvascular decompression (MVD), among the several other surgical options, for treating refractory classical trigeminal neuralgia (TN) relies mostly on preoperative imaging, but the degree of reliability of MRI remains a matter of debate. The authors approached the question of predictability of neurovascular conflict (NVC) in a series of 100 protocolized MRI studies from patients with TN who underwent MVD, by reexamination of MR images, blinded to the clinical data and surgical findings, including the side of the neuralgia.

METHODS

Patients included in the study were those who underwent MVD after surgical indication had been determined based on a protocolized imagery workup (3D high-resolution T2-weighted cisternography centered on the trigeminal nerve, 3D time-of-flight angiography, and 3D gadolinium-enhanced T1-weighted imaging) performed at our institution. All MR images were blindly reexamined, and neurovascular relationships were described on both sides, noting the existence of compression, vessels involved, situation along the root, and degree of compression. The results of MRI evaluation were then compared with actual surgical findings. The extent of agreement and quality of the prediction were expressed with Cohen's kappa coefficient (κ) and receiver operating characteristic (ROC) statistics.

RESULTS

A conflict had actually been found during surgery in 94 of 100 patients. The sensitivity of MRI to detect a conflict was 97% and the specificity was 50%. Vessel type was identified with high reliability (κ = 0.80), while the grade of the conflict and its situation along the root showed poor to average reliability (κ = 0.38 and κ = 0.40, respectively). The area under the ROC curve for predicting the presence of a conflict according to the grades of conflict seen on MRI was 0.93, which is considered very good. The positive predictive value was differentiated according to the grade of conflict, with a very high value for high grades of vascular conflict.

CONCLUSIONS

This study shows an overall good reliability of MRI to predict the existence of an NVC. The prediction value is excellent for high grades of compression. Some apparent low-grade compressions on MRI may be revealed as false positives in surgical exploration. This raises the question of what other imaging methods might be used to determine not only the existence of a conflict but also its degree of compression. The degree of compression is of paramount importance to predict the probability of long-term pain relief, and therefore in the decision to propose MVD as the first choice of surgical treatment.

High-resolution heavily T2-weighted magnetic resonance imaging for evaluation of the pituitary stalk in children with ectopic neurohypophysis

BACKGROUND

In anterior pituitary deficiency, patients with non visible pituitary stalk have more often multiple deficiencies and persistent deficiency than patients with visible pituitary stalk.

OBJECTIVE

To compare the diagnostic value of a high-resolution heavily T2-weighted sequence to 1.5-mm-thick unenhanced and contrast-enhanced sagittal T1-weighted sequences to assess the presence of the pituitary stalk in children with ectopic posterior pituitary gland.

MATERIALS AND METHODS

We retrospectively evaluated the MRI data of 14 children diagnosed with ectopic posterior pituitary gland between 2010 and 2014. We evaluated the presence of a pituitary stalk using a sagittal high-resolution heavily T2-weighted sequence and a 1.5-mm sagittal T1-weighted turbo spin-echo sequence before and after contrast medium administration.

RESULTS

A pituitary stalk was present on at least one of the sequences in 10 of the 14 children (71%). T2-weighted sequence depicted the pituitary stalk in all 10 children, whereas the 1.5-mm-thick T1-weighted sequence depicted 2/10 (20%) before contrast injection and 8/10 (80%) after contrast injection (P=0.007).

CONCLUSION

Compared with 1.5-mm-thick contrast-enhanced T1-weighted sequences, high-resolution heavily T2-weighted sequence demonstrates better sensitivity in detecting the pituitary stalk in children with ectopic posterior pituitary gland, suggesting that contrast injection is unnecessary to assess the presence of a pituitary stalk in this setting.