Neil Dorward

Clinical validation of true frameless stereotactic biopsy: analysis of the first 125 consecutive cases.

OBJECTIVEA lockable guide device, adjustable for positioning, was used to obtain samples for tissue analysis during brain biopsy procedures performed using an interactive image guidance system. Clinical validation of this technique, which was developed for true frameless stereotactic biopsies, and analyses of the histological yield, complication rate, and patient demographic characteristics for a large series of frameless stereotactic biopsies were the purposes of this study. METHODSDemographic, radiological, surgical, and clinical data were prospectively collected for a series of 125 frameless stereotactic biopsies performed using the technique described in detail previously. RESULTSEighty-six procedures were magnetic resonance imaging-directed and 39 were computed tomography-directed. The mean diameter of the biopsied lesions was 36 mm, and the mean distance from the skin was 35.8 mm. Sixteen percent of the patients harbored multiple lesions, and 5.6% of the biopsied lesions were infratentorial. The mean operative time (including the entire anesthetic time) was 1.5 hours. The smear examination findings were corroborated by conclusive histological results in 96% of the cases, and definitive positive diagnoses were obtained in 122 cases (97.6%). Ten patients experienced surgical complications, but the sustained morbidity rate was 2.4% (including the death of a patient who was in critical clinical condition preoperatively and who died 2 mo later as a result of a chest infection; mortality rate, 0.8%). CONCLUSIONThis true frameless stereotactic biopsy technique was associated with low morbidity and mortality rates and an excellent diagnostic yield, with overall results at least as good as those observed for frame-based stereotaxy. The excellent accuracy results demonstrated previously and statistically significant reductions in operative time, as well as improved image presentation, target selection, and simplicity, support the use of this frameless stereotactic technique in preference to frame-based biopsy techniques.

Endocrine outcomes in Endoscopic Pituitary Surgery: A Literature Review

BackgroundSince the introduction of fully endoscopic surgery this new technique has been adopted with enthusiasm by many but not all pituitary surgeons. Whilst some advantages of minimal access have been recognised, the information on endocrine outcomes has been slow to accumulate.MethodThis literature review examined all the endoscopic papers for endocrine results and complication rates. Where adequate detail was provided these results were broken down by subtype and the pooled cure rates calculated.FindingsThe review revealed that the fully endoscopic method is the equal of the microscopic technique for endocrine remission in functioning pituitary tumours. Furthermore the endoscopic results in functioning macroadenomas are substantially better than the microscopic results with similar complication rates.ConclusionsEndoscopic pituitary surgery offers significant advantages over the microscopic technique and should become the standard method of pituitary adenoma surgery.

Clinical introduction of an adjustable rigid instrument holder for frameless stereotactic interventions.

Interactive image guidance is now in routine use for open neurosurgical procedures and has demonstrated patient benefits. However, freehand interactive guidance is not an appropriate replacement for the traditional frame-based stereotactic procedures of biopsy, electrode placement, and functional lesioning. These point-based procedures require precise target localization and direct instrument guidance to avoid collateral brain injury. To perform true frameless stereotactic procedures requires a guide that is also adjustable for positioning, lockable, and adaptable to multiple instruments. We describe such a device, which is employed for the guidance of biopsy needles, shunts, electrodes, and endoscopes during neuronavigation. The method of frameless stereotactic biopsy retrieval with an infrared-based neuronavigation system is described, clinical results are given, and further areas of application discussed.

Lymphocytic hypophysitis presenting early in pregnancy

Sirs: A 31 year old woman presented following the development of worsening vision in both eyes for two weeks, associated with nausea, vomiting and tiredness. There had been a mild headache for the previous three weeks, worse in the morning, without symptoms suggestive of raised intracranial pressure. She was in her 22nd week of pregnancy. There were no other symptoms, and previously she had been well. This was her second pregnancy, the first having completed at term some nine months previously. She had breastfed for six weeks, and the baby was well. Her past medical history was unremarkable. On examination she was well. Blood pressure was 100/60 without a postural drop. The cardiovascular and respiratory examinations were normal. The abdominal examination revealed a gravid uterus of expected size. The higher cortical functions were normal. The visual acuities were 6/6 on the right with normal colour vision, 6/36 on the left with absent colour vision and a relative afferent pupillary defect. The visual fields are shown in Fig. 1. Ocular examination was normal and the discs appeared normal. Trigeminal sensory function and the remainder of the neurological examination were normal.

Precise Cannulation of the Foramen Ovale in Trigeminal Neuralgia Complicating Osteogenesis Imperfecta with Basilar Invagination: Technical Case Report

OBJECTIVE AND IMPORTANCE Trigeminal neuralgia is a rare feature of basilar invagination, which is itself a complication of osteochondrodysplastic disorders. Microvascular decompression is an unattractive option in medically refractory cases. The conventional percutaneous approach to the trigeminal ganglion is anatomically impossible because the foramen ovale points inferiorly and posteromedially. We report a new technique for image-guided trigeminal injection in a patient with basilar invagination complicating osteogenesis imperfecta. CLINICAL PRESENTATION A 26-year-old woman with osteogenesis imperfecta presented with a 3-year history of typical left maxillary division trigeminal neuralgia, which was poorly controlled by carbamazepine at the maximum tolerated dose. She had obvious cranial deformities, left optic atrophy, delayed left eye closure, tongue atrophy, but normal facial sensation and corneal reflexes. A computed tomographic scan and magnetic resonance imaging confirmed severe basilar invagination. TECHNIQUE Frameless stereotactic glycerol injection of the left trigeminal ganglion was performed under general anesthesia using the infrared-based EasyGuide Neuro system (Philips Medical Systems, Best, The Netherlands) with magnetic resonance imaging and computed tomographic registration. The displaced and distorted left foramen ovale was cannulated via a true frameless stereotactic method with the trajectory determined by virtual pointer elongation. The needle placement was confirmed with injection of contrast medium into the trigeminal cistern. The path needed to enter the foramen traversed the right cheek, soft palate, and left tonsil. The patient went home pain-free with a preserved corneal reflex and no complications. CONCLUSION Frameless stereotaxy allows customization to individual patient anatomy and may be adapted to a variety of percutaneous procedures used in areas where the anatomy is complex.

Preliminary investigation into the use of ultrasound elastography during brain tumour resection

Introduction Differentiation of brain tumours from normal brain, during surgical resection is, in part, based on their differing mechanical properties. Brain tumours have variable stiffness characteristics. Surgical evaluations on stiffness are, at best, subjective. Ultrasound elastography is a non-invasive method for imaging mechanical properties of tissues such as stiffness at depth. It is hypothesized that this technique may assist in differentiating tumour from the brain in an intraoperative setting. Methods This study evaluated the feasibility of the intraoperative use of ultrasound elastography during brain tumour resection. A total of 24 patients were recruited for the study. Surgical findings on tumour stiffness were compared with the elastogram findings. Furthermore, visibility of the brain-tumour interface on ultrasound echography compared with ultrasound elastography was analysed. Results Ultrasound elastography was found to have a sensitivity of 100% and specificity of 75% at detecting that tumour had a different stiffness to the brain when compared with surgical findings. The technique was also found to have a 100% sensitivity and specificity at the detection of intratumoral stiffness heterogeneity compared with surgical findings. The presence of fluid-filled cysts limited the quality of the elastograms. Ultrasound elastography did not detect the brain-tumour interface as accurately as conventional echography. Conclusion These findings suggest that ultrasound elastography in combination with conventional B-mode ultrasound may be a useful adjunct to differentiate tumour from the brain.

A novel technique of detecting MRI-negative lesion in focal symptomatic epilepsy: Intraoperative ShearWave Elastography

Focal symptomatic epilepsy is the most common form of epilepsy that can often be cured with surgery. A small proportion of patients with focal symptomatic epilepsy do not have identifiable lesions on magnetic resonance imaging (MRI). The most common pathology in this group is type II focal cortical dysplasia (FCD), which is a subtype of malformative brain lesion associated with medication‐resistant epilepsy. We present a patient with MRI‐negative focal symptomatic epilepsy who underwent invasive electrode recordings. At the time of surgery, a novel ultrasound‐based technique called ShearWave Elastography (SWE) was performed. A 0.5 cc lesion was demonstrated on SWE but was absent on B‐mode ultrasound and 3‐T MRI. Electroencephalography (EEG), positron emission tomography (PET), and magnetoencephalography (MEG) scans demonstrated an abnormality in the right frontal region. On the basis of this finding, a depth electrode was implanted into the lesion. Surgical resection and histology confirmed the lesion to be type IIb FCD.

Real-time ultrasound elastography in neurosurgery

This study furthers previous work by this group [1] on the use of ultrasound elastography intra-operatively in the brain. Real-time 2-dimensional (2D) ultrasound elastograms were acquired during neurosurgical operations for brain and spinal cord tumors, and, in select cases, approximately real-time 3-dimensional (3D) elastograms (volumes of axial strain data) were acquired in the brain. For the first time, elastograms were successfully generated in the spinal cord using vascular pulsations to generate internal strains. The results revealed strain data that correlated well with the surgeons assessment of the stiffness of the tissues, and areas of reduction in cross-correlation coefficient and very high axial strain at tumor boundaries were found to correspond to cleavage planes. Off-line axial normal strain and axial shear strain calculation assisted in image interpretation. Benefits of this method in neurosurgery include pre-informing the surgeon as to the stiffness of the lesion and identification of dissection planes, both of which can lead to safer surgery.

Intra-operative Ultrasound Elastography and Registered Magnetic Resonance Imaging of Brain Tumours: A Feasibility Study

Following craniotomy, the decision to resect a brain tumour is based on (1) the surgeons interpretation of preoperative imaging, such as MRI, (2) correlating the imaging to the surgical field, (3) visual inspection of the surgical field, and (4) palpation thus providing biomechanical information on tumour and brain. There is a degree of subjectivity in the use of palpation for biomechanical evaluation. Ultrasound elastography is a technique for determining more objective biomechanical information at depth in the form of relative strain, thus indirectly stiffness, within an ultrasound scan plane. In addition, neuro-navigation techniques assist in correlating preoperative imaging to the surgical field. We present two cases where ultrasound elastography with co-registered MRI, using neuro-navigation, was used intra-operatively during brain tumour resection. Correlation with the co-registered MRI was excellent in both patients. Strain contrast between brain and tumour was evident in elastograms produced in both patients; the tumour had a lower strain, hence was stiffer compared with brain. When strain applied was increased slip between tumour and brain was detected. All these findings corresponded with the surgical findings. Ultrasound elastography with co-registered MRI is a promising imaging technique, which can be used intra-operatively to provide biomechanical information prior to resection.

Slip elastography: A novel method for visualising and characterizing adherence between two surfaces in contact

Identification of the anatomical location and mechanical properties such as adherence at the tissue tumour interface may be of clinical benefit in determination of tumour resectability and prognosis. There are currently no imaging modalities in routine clinical practice that can provide this information. This paper presents the development of a new imaging technique based on ultrasound elastography, called slip elastography, for determination of the anatomical location and measurement of the adherence between two surfaces. The theoretical basis of slip and its definition in relation to shear are described. In vitro testing with gelatine phantoms to determine the optimal parameters for shear strain estimation and slip boundary measurement and to test reliability are also described. The results suggest that slip elastography can reliably identify the anatomical location of a slip boundary and can measure the externally applied axial force required to initiate slip at that boundary in vitro. The vector based shear strain estimator was the most robust and worked with minimal angular dependence with minimal non-slip shearing artefact.