Radiological follow-up of endovascularly treated intracranial aneurysms: a survey of current practice in the UK and Ireland.

PURPOSE: Due to the risk of intracranial aneurysm (IA) recurrence and the potential requirement for re-treatment following endovascular treatment (EVT), radiological follow-up of these aneurysms is necessary. There is little evidence to guide the duration and frequency of this follow-up. The aim of this study was to establish the current practice in neurosurgical units in the UK and Ireland. METHODS: A survey was designed with input from interventional neuroradiologists and neurosurgeons. Neurovascular consultants in each of the 30 neurosurgical units providing a neurovascular service in the UK and Ireland were contacted and asked to respond to questions regarding the follow-up practice for IA treated with EVT in their department. RESULTS: Responses were obtained from 28/30 (94%) of departments. There was evidence of wide variations in the duration and frequency of follow-up, with a minimum follow-up duration for ruptured IA that varied from 18 months in 5/28 (18%) units to 5 years in 11/28 (39%) of units. Young patient age, previous subarachnoid haemorrhage and incomplete IA occlusion were cited as factors that would prompt more intensive surveillance, although larger and broad-necked IA were not followed-up more closely in the majority of departments. CONCLUSIONS: There is a wide variation in the radiological follow-up of IA treated with EVT in the UK and Ireland. Further standardisation of this aspect of patient care is likely to be beneficial, but further evidence on the behaviour of IA following EVT is required in order to inform this process.

A survey of the radiological follow-up of unruptured intracranial aneurysms in the United Kingdom.

OBJECTIVE: Unruptured intracranial aneurysms (UIA) are common. For many the treatment risks outweigh their risk of subarachnoid haemorrhage and patients undergo surveillance imaging. There is little data to inform if and how to monitor UIAs resulting in widely varying practices. This study aimed to determine the current practice of unruptured UIA surveillance in the United Kingdom. METHODS: A questionnaire was designed to address the themes of surveillance protocols for UIA including when surveillance is initiated, how frequently it is performed, and when it is terminated. Additionally, how aneurysm growth is managed and how clinically meaningful growth is defined were explored. The questionnaire was distributed to members of the British Neurovascular Group using probability-based cluster and non-probability purposive sampling methods. RESULTS: Responses were received from 30 of the 30 (100.0%) adult neurosurgical units in the United Kingdom of which 27 (90.0%) routinely perform surveillance for aneurysm growth. Only four units had a unit policy. The mean patient age up to which a unit would initiate follow-up of a low-risk UIA was 65.4 ± 9.0 years. The time points at which imaging is performed varied widely. There was an even split between whether units use a fixed duration of follow-up or an age threshold for terminating surveillance. Forty percent of units will follow-up patients more than 5 years from diagnosis. The magnitude in the change in size that was felt to constitute growth ranged from 1 to 3mm. No units routinely used vessel wall imaging although 27 had access to 3T MRI capable of performing it. CONCLUSIONS: There is marked heterogeneity in surveillance practices between units in the United Kingdom. This study will help units better understand their practice relative to their peers and provide a framework forplanning further research on aneurysm growth.

Comparison between outcomes of endovascular and surgical treatments of ruptured anterior communicating artery aneurysms.

INTRODUCTION: The natural history and optimal treatment of previously ruptured anterior communicating artery (ACOM) aneurysms that recur is unknown. This study looks at rates of complications and recurrences of ruptured ACOM aneurysms treated endovascularly and surgically. MATERIALS AND METHODS: A retrospective observational study of all patients presenting to a single tertiary neurosurgical centre with the first presentation of subarachnoid haemorrhage (SAH) secondary to a ruptured ACOM aneurysm. Data was collected from November 2012 to September 2018 and included baseline demographics, aneurysm characteristics, management, complications, follow-up imaging, and clinical outcomes. RESULTS: 137 patients were included in the study. 113 aneurysms were coiled and 19 were clipped. Management decisions were taken by the multidisciplinary team based on aneurysm morphology or the presence of a haematoma exerting mass effect. There were 187.5 patient-years of follow-up, with a median of 3 years (range 0-73 months). Rates of vasospasm, infarction, CSF diversion, rebleed, length of stay, and functional outcome were not significantly different in the two cohorts. There was a statistically significant increase in the risk of ACOM recurrence in the coiled group when compared to the clipped group at one year (p = .0433). 15 patients required further treatment at a median time of 16 months. In a subgroup group analysis of coiled aneurysms, there was no statistical differences in rates of rebleeding or the functional outcome in those that had aneurysm recurrence and those that did not. CONCLUSIONS: This study suggests patients with aneurysms treated by endovascular coiling have an increased risk of recurrence versus those treated with clipping. However, the risk of rebleed was not statistically significant. The prevention and impact of recurrence and residual aneurysms remains incompletely understood. Hence, treatment decisions should be taken by patients after they have been given carefully considered recommendations from the multi-disciplinary team.

Mini-Pterional Craniotomy for Microsurgical Ligation of a Sylvian Fissure Arteriovenous Fistula.

Pial arteriovenous fistulae (pAVF) are rare lesions, arising from direct fistulation between an artery and vein, with absence of a nidus. We present the surgical treatment of a 22-year-old female found to have a right middle cerebral artery (MCA) pAVF in the Sylvian fissure. The patient underwent a right mini-pterional approach, and careful dissection of the arterial feeder, venous varix and fistulation point. The fistulation point was tested with a temporary clip and intra-operative indocyanine green (ICG) videoangiography. All arterial feeders were identified and ligated. Complete obliteration was confirmed using ICG and post-operative digital subtraction angiography (DSA). The patient made a good recovery with no neurological deficits, and her pulsatile tinnitus stopped. Pial arteriovenous fistulae are rare lesions amenable for a surgical cure in the appropriate context.

A method for recording resistance changes non-invasively during neuronal depolarization with a view to imaging brain activity with electrical impedance tomography.

Electrical impedance tomography (EIT) is a recently developed medical imaging method which has the potential to produce images of fast neuronal depolarization in the brain. The principle is that current remains in the extracellular space at rest but passes into the intracellular space during depolarization through open ion channels. As current passes into the intracellular space across the capacitance of cell membranes at higher frequencies, applied current needs to be below 100 Hz. A method is presented for its measurement with subtraction of the contemporaneous evoked potentials which occur in the same frequency band. Neuronal activity is evoked by stimulation and resistance is recorded from the potentials resulting from injection of a constant current square wave at 1 Hz with amplitude less than 25% of the threshold for stimulating neuronal activity. Potentials due to the evoked activity and the injected square wave are removed by subtraction. The method was validated with compound action potentials in crab walking leg nerve. Resistance changes of -0.85+/-0.4% (mean+/-SD) occurred which decreased from -0.97+/-0.43% to -0.46+/-0.16% with spacing of impedance current application electrodes from 2 to 8 mm but did not vary significantly with applied currents of 1-10 microA. These tallied with biophysical modelling, and so were consistent with a genuine physiological origin. This method appears to provide a reproducible and artefact free means for recording resistance changes during neuronal activity which could lead to the long-term goal of imaging of fast neural activity in the brain.