Biomedical subjects

William Harkness

Publications and source records attributed to William Harkness.

13 recordsLinked to original sources

PubMed2006

Temporal lobe resections.

INTRODUCTION: In the 50 years since Penfield outlined the requirements of the epilepsy surgeon, we have seen the introduction of the digitised electroencephalogram (EEG), video telemetry and the magnetic resonance imaging (MRI) scan. In the operating room, advances in neuro-anaesthesia, the introduction of the operating microscope, image guidance and the ultrasonic aspirator have greatly enhanced the surgeons' technical ability. Despite these changes, the thesis encapsulated in Penfield's statement is that the surgeon needs to understand and interpret the preoperative data in such a way as to identify as closely as possible the epileptogenic zone where he must carry out surgery with the utmost care and diligence, and finally, in the context of audit and follow-up of his surgical patients, he must be able to predict for each individual case the likelihood of success and failure of any particular procedure. CONCLUSION: Previous articles in this supplement have looked at the specific investigations carried out to identify the epileptogenic zone, but once this data has been gathered, it is the responsibility of the neurosurgeon, within the context of the multidisciplinary team, to decide whether surgery is both feasible and advisable and then to discuss this in depth with the patient and their family and carers. The multidisciplinary epilepsy surgery meeting allows cases to be discussed in an open forum and the decisions made in this meeting can then be discussed with the family. The process of consent will begin from the moment any surgical procedure is discussed and should, wherever possible, be reinforced with written, as well as verbal, information. The process of consent should be a continuum until the actual day of surgery. All parties involved in the care and management of the patient should be regarded as stakeholders in this decision, and it is vital that all these stakeholders are working towards a common goal. OBJECTIVES: In this article, I will consider the specific aspects of the presurgical investigations that are applicable to the temporal lobe and the differing types of surgery that are likely to be indicated. I will then describe, in detail, the surgical technique of temporal lobe resection, highlighting some of the pitfalls and successes that such surgery can provide.

Epilepsy, Temporal Lobe↗

PubMed2006

Predicting memory decline following epilepsy surgery: a multivariate approach.

BACKGROUND: While some patients experience a decline in memory function following an anterior temporal lobe resection, there is considerable individual variation in the extent, nature, and direction of postoperative memory change. Patients with surgically remediable temporal lobe epilepsy differ in etiology, the extent and type of underlying pathology, and on demographic and epilepsy-related variables, all of which may have an impact on their pre- and postoperative neuropsychological functioning. This study examined the relationship between these variables and postoperative memory decline. METHODS: Logistic regression was used to examine the effects of age, laterality of surgery, age of onset of epilepsy, underlying pathology and preoperative level of memory function on postoperative verbal learning in 288 patients who had undergone an anterior temporal lobe resection. One hundred twenty-five patients underwent a right temporal lobe resection (RTL), 163 patients underwent a left temporal lobe resection (LTL). RESULTS: In the group as a whole, 25% of the patients demonstrated a significant postoperative deterioration in verbal learning. Postoperative deterioration in verbal learning was significantly associated with higher levels of preoperative function in both the RTL and LTL groups. Older age at the time of the operation and a lower verbal IQ were additional significant predictors for the RTL group. The presence of cortical dysgenesis was a significant predictor of postoperative decline in the LTL group. The logistic regression models accurately identified 3/4 of those who experienced a postoperative decline in memory, using a cutoff of 0.25 or above to identify high risk. CONCLUSIONS: Our analyses suggest that the majority of patients with a high risk of significant postoperative memory decline can be reliably identified preoperatively. These models are valuable tools helping patients make an informed decision regarding surgery.

Epilepsy↗

PubMed2005

Isolated diastasis of cranial sutures: unusual presentation of a blocked shunt in an infant.

INTRODUCTION: Ventriculo-peritoneal (VP) shunt malfunction is usually due to blockage of the ventricular catheter and this is typically apparent as enlarged ventricles on a CT scan of the brain. We describe a less common radiological finding in an infant with a blocked shunt. CASE REPORT: A male infant presenting with hydrocephalus in the neonatal period underwent insertion of a VP shunt. He represented at 17 months of age with the clinical features of raised intracranial pressure. A CT scan of the brain revealed that the ventricles were smaller compared with his previous scan, but X-rays taken as part of the shunt series revealed diastasis of the sagittal, coronal and lambdoid sutures. The shunt was explored and the ventricular catheter was found to be blocked and was replaced. Post-operatively there was complete resolution of the symptoms and the suture diastasis. CONCLUSIONS: Suture diastasis with small ventricles on a CT scan of the brain is an unusual radiological finding in an infant with a blocked shunt. Suture diastasis in this patient suggests raised intracranial volume and this may be due to the transependymal absorption of CSF into the white matter.

Cerebrospinal Fluid Shunts↗

PubMed2005

Percutaneous coagulation of choroid plexus to unblock the ventricular catheter using the Seldinger technique: preliminary report.

BACKGROUND: Blockage of the ventricular catheter is the most common reason for shunt malfunction and is usually due to ingrowth of choroid plexus into the catheter lumen. The authors describe a simple technique to unblock the ventricular catheter in situ. METHODS: In children with symptoms and radiological evidence of shunt malfunction, the Rickham reservoir was tapped under a general anesthetic. Manometry with saline was performed to confirm isolated proximal blockage of shunt. A guide wire, insulated to the scalp, was passed into the ventricular catheter using the Seldinger technique. Bursts of monopolar diathermy were applied to the guide wire to coagulate choroids plexus and manometry was repeated. In this preliminary study, all ventricular catheters were subsequently revised. RESULTS: This percutaneous technique was undertaken in 7 children with confirmed proximal shunt malfunction. Successful unblocking of the ventricular catheter was established by increased flow of cerebrospinal fluid around the guide wire. The mean +/- SEM manometry reading post-diathermy (21.9 +/- 5 cm) was higher than the pre-diathermy value (0.6 +/- 0.6 cm; P < .01). CONCLUSIONS: Percutaneous coagulation of the choroids plexus using the Seldinger technique is a simple, inexpensive, minimally invasive method to unblock ventricular catheters and it may be suitable as a stand-alone technique in selected patients.

Adolescent↗

PubMed2005

Reliable registration of preoperative MRI with histopathology after temporal lobe resections.

PURPOSE: Conventional and novel magnetic resonance imaging (MRI) techniques can detect cerebral abnormalities in patients with refractory focal epilepsies. Correlation of preoperative MRI and histopathology is important to validate MRI findings, but in practice is far from straightforward. Peroperative neuronavigation and placement of markers on tissue is of limited use in temporal lobe resections. MRI scanning of the resected specimen for registration with in vivo MRI is complicated by anisotropic tissue deformation. We have developed a method to facilitate registration of preoperative MRI with the resected specimen and to enable correlation of MRI findings with histopathology. METHODS: Sixteen en bloc temporal lobe resections undertaken for refractory temporal lobe epilepsy were studied. The specimens were fixed in formalin and then cut coronally by using a cradle with parallel blades at 5-mm intervals to ensure evenly thick tissue slices in the same orientation. Volumetric T1-weighted preoperative MRIs were reformatted, and consecutive slices (0.94 mm) cut in the same orientation as the resected lobe were visually compared with photographs of tissue slices by two independent observers. RESULTS: In 15 (94%) of 16 cases, a <2-mm difference was found between the two observers' matches of MRI slices with tissue slices. In the last case, a 4-mm difference was noted. In all cases, a consensus was reached by the two observers. The suggested MRI-histology matches were within the resections seen on postoperative scans. CONCLUSIONS: Careful labelling and postoperative handling and slicing ensured histopathologic tissue slices of uniform thickness and slicing angle. This technique can be applied to a range of MRI datasets, enabling exploration of the pathologic basis of abnormalities on conventional and novel MRI acquisitions.

Anterior Temporal Lobectomy↗

PubMed2005

Microarray analysis of pediatric ependymoma identifies a cluster of 112 candidate genes including four transcripts at 22q12.1-q13.3.

Ependymomas are glial cell-derived tumors characterized by varying degrees of chromosomal abnormalities and variability in clinical behavior. Cytogenetic analysis of pediatric ependymoma has failed to identify consistent patterns of abnormalities, with the exception of monosomy of 22 or structural abnormalities of 22q. In this study, a total of 19 pediatric ependymoma samples were used in a series of expression profiling, quantitative real-time PCR (Q-PCR), and loss of heterozygosity experiments to identify candidate genes involved in the development of this type of pediatric malignancy. Of the 12,627 genes analyzed, a subset of 112 genes emerged as being abnormally expressed when compared to three normal brain controls. Genes with increased expression included the oncogene WNT5A; the p53 homologue p63; and several cell cycle, cell adhesion, and proliferation genes. Underexpressed genes comprised the NF2 interacting gene SCHIP-1 and the adenomatous polyposis coli (APC)-associated gene EB1 among others. We validated the abnormal expression of six of these genes by Q-PCR. The subset of differentially expressed genes also included four underexpressed transcripts mapping to 22q12.313.3. By Q-PCR we show that one of these genes, 7 CBX7(22q13.1), was deleted in 55% of cases. Other genes mapping to cytogenetic hot spots included two overexpressed and three underexpressed genes mapping to 1q31-41 and 6q21-q24.3, respectively. These genes represent candidate genes involved in ependymoma tumorigenesis. To the authors' knowledge, this is the first time microarray analysis and Q-PCR have been linked to identify heterozygous/homozygous deletions.

Brain Neoplasms↗

PubMed2003

Intraventricular migration of a Rickham reservoir: endoscopic retrieval.

CASE REPORT: An unusual case of the intraventricular migration of a Rickham reservoir in a child and its subsequent removal by endoscopy is described. A newborn boy presenting with hydrocephalus secondary to intraventricular haemorrhage, had a Rickham reservoir inserted through a frontal burr hole, made adjacent to the anterior fontanel. Later, serial CT scans of the brain over a 3-year period revealed progressive migration of the Rickham reservoir into the lateral ventricle and then into the third ventricle. As the ventricles were also enlarged, they were explored endoscopically and the Rickham reservoir was removed. DISCUSSION: Intracranial migration of a Rickham reservoir is rare. It is suggested that the placement of a small burr hole, away from the fontanels and growing sutures and the use of anchoring sutures to hold the reservoir to the periosteum are important steps in avoiding this unusual complication.

Cerebral Hemorrhage↗

PubMed2003

Current status of surgery in the management of epilepsy.

PURPOSE: To review systematically the available evidence with regard to the current status of epilepsy surgery in the management of patients with epilepsy. METHODS: A careful search of published literature, including Medline, published reviews, chapters, and cross-references thereof. RESULTS: With medical treatment of epilepsy being unsuccessful in many cases, the importance of surgical approaches cannot be underscored. Early surgery is the treatment of choice for patients with clear-cut mesial temporal sclerosis and results in significant clinical improvement in up to 80% of cases, provided the EEG, neuropsychological, and neuropsychiatric results are in concordance with this approach. In patients with poorly defined, widespread, or dual pathology, however, invasive recordings may be necessary, and while this is performed in major centres, the outcome is rather more variable in this group. Improved surgical techniques, and the use of stereotactic approaches and image guidance procedures, have resulted in surgical resections becoming more selective. With isolated structural lesions such as dysembryoplastic tumours, low-grade astrocytomas, or focal vascular abnormalities, total macroscopic and radiological evidence of lesional excision is associated with excellent seizure-free outcome. The first randomised controlled trial of epilepsy surgery has demonstrated clearly the efficacy of these techniques, and the risk of complications. DISCUSSION: Increasing sophistication of noninvasive presurgical evaluation enables surgical candidates to be identified at an earlier stage and presents a realistic alternative to medical treatment in many cases. The introduction of minimally invasive techniques has had a significant impact on surgical practice and its associated morbidity. The future of epilepsy surgery lies with continued basic science research and its application to clinical medicine.

Epilepsy↗

PubMed2003

The natural history of ventriculomegaly and tonsillar herniation in children with posterior fossa tumours--an MRI study.

OBJECTIVE: Posterior fossa tumours in children predispose to hydrocephalus, although the natural history is unclear and the need for drainage of the ventricles is controversial. We report on the natural history of ventriculomegaly and tonsillar herniation, as seen on serial MRI scans in children with posterior fossa tumours. RESULTS: Eighty-nine children with posterior fossa tumours were reviewed retrospectively. Overall, 18 (20%) patients required permanent cerebrospinal fluid (CSF) drainage in the form of a ventriculoperitoneal shunt (n = 15) or third ventriculostomy (n = 3). On pre-operative MRI scan, the ventricular size was assessed by measurement of the ventricular index (VI) and 59 patients (66%) had a VI greater than 0.4. There was a progressive decrease in the mean VI from pre-operative to post-operative MRI scans and beyond 3-9 months after surgery, the mean VI was less than 0.4 (p = 0.0001). Patients requiring permanent CSF drainage had a greater VI pre-operatively and at 3-9 months post-operatively (p < 0.05). On pre-operative MRI scan, 75 patients (84%) had greater than 5 mm herniation of the cerebellar tonsils below the level of the foramen magnum. There was a progressive decrease in the mean tonsillar herniation from pre-operative to post-operative MRI scans, with time (p = 0.0001), although this did not relate to the need for CSF drainage. On multivariate analysis, the need for permanent CSF drainage was associated with pre- and intra-operative CSF drainage (odds ratio = 23.3; p = 0.0001) and incomplete surgical excision of tumour (odds ratio = 7.7; p = 0.006). CONCLUSIONS: Hydrocephalus and tonsillar herniation are common in children with posterior fossa tumours, although post-operatively there is a natural tendency for it to resolve and only a fifth of the patients needed permanent CSF drainage. We recommend selective drainage of CSF in children with posterior fossa tumours. Patients at risk are those with severe symptoms at presentation, needing peri-operative CSF drainage and those with subtotal resection of tumour.

Adenoids↗

PubMed2002

Diffusion tensor imaging in refractory epilepsy.

Diffusion tensor imaging is an imaging method that is sensitive to the molecular movement of water, which indicates cellular integrity and pathology. A patient with refractory epilepsy and normal conventional MRI was examined with diffusion tensor imaging. An area of abnormal diffusion in the right frontal lobe was identified and surgically resected. The patient had a good clinical outcome. Histopathological examination of the resected tissue showed gliosis. Our findings may affect the investigation of similar patients, and provide histopathological confirmation of diffusion abnormalities.

Adult↗

PubMed2002

Cytoarchitectural abnormalities in hippocampal sclerosis.

Hippocampal sclerosis (HS) is the most common pathological substrate for temporal lobe epilepsy with a characteristic pattern of loss of principle neurons primarily in CA1 and hilar subfields. Other cytoarchitectural abnormalities have been identified in human HS specimens, including dispersion of dentate granule cells and cytoskeletal abnormalities in residual hilar cells. The incidence of these features, their relationship to the severity of HS and potential indication of underlying hippocampal maldevelopment is unverified. In a series of 183 hippocampectomies we identified classical HS (grades 3 and 4) in 90% of specimens, granule cell disorganization or severe dispersion in 40% of cases with a bilaminar pattern in 10%, and cytoskeletal abnormalities in hilar cells in 55% of cases. The severity of granule cell disorganization correlated closely with the degree of hippocampal neuronal loss but not with the age at first seizure or a history of a precipitating event for epilepsy such as prolonged febrile seizures. These findings suggest that granule cell disorganization is closely linked with the progression of HS rather than a hallmark of impaired hippocampal maturation. Furthermore, stereological quantitation of granule cells showed evidence of cell loss but greater numbers in regions of maximal dispersion, which may indicate enhanced neurogenesis of these cells. Quantitation of reelin-and calretinin-positive Cajal-Retzius cells in the dentate gyrus molecular layer in 26 cases showed no correlation between the number of these cells and the severity of granule cell dispersion, but increased numbers of these cells were present in HS with respect to control groups. Although a role for Cajal-Retzius cells is therefore not implicated in the mechanism of granule cell disorganization, their excess number may be indicative of underlying hippocampal maldevelopment in HS.

Adolescent↗

PubMed2002

Intractable epilepsy and olfactory bulb hamartoma. A case report.

The objective of this case report is to demonstrate that a benign tumour arising solely from the olfactory bulb can act as a primary epileptic focus and to illustrate the difficulty in making a preoperative diagnosis of pathological lesions in this area. The case of a 29-year-old male with intractable epilepsy is presented. Radiological imaging demonstrated a conspicuous, calcified lesion in the mesial inferior frontal lobe. Electroclinical findings confirmed this to be the epileptogenic zone. Surgery and subsequent histology surprisingly revealed this focal lesion to be a benign hamartoma arising solely from the olfactory bulb. Resection resulted in seizure resolution. Tumours of the olfactory apparatus are extremely rare, but can present with epilepsy.

Adult↗

PubMed2002

Surgical procedures for posterior fossa tumors in children: does craniotomy lead to fewer complications than craniectomy?

OBJECT: Traditionally, access to the posterior fossa involved a suboccipital craniectomy. More recently, posterior fossa craniotomies have been described, although the long-term benefits of this procedure are not clear. The authors compared the postoperative complications of craniectomies and craniotomies in children with posterior fossa tumors. METHODS: From a total of 110 children undergoing surgery for posterior fossa tumors, 56 underwent craniectomy and 54 had a craniotomy. The mean duration of the hospital stay was longer in the craniectomy group (17.5 compared with 14 days). At operation, similar numbers of patients in both groups had total macroscopic clearance of the tumor, complete dural closure, and duraplasty. Postoperatively, more patients in the craniectomy group were noted to have cerebrospinal fluid (CSF) leakage (27 compared with 4%; p < 0.01) and pseudomeningoceles (23 compared with 9%; p < 0.05). There was no significant difference between the two groups in the numbers of patients with CSF infections, wound infections, or hydrocephalus requiring permanent CSF drainage. Patients with CSF leaks had a longer duration of hospital stay (20.7 compared with 14.9 days; p < 0.01), and were more likely to have CSF infections (35 compared with 12%; p < 0.01) and wound infections (24 compared with 1%; p < 0.01) than patients without CSF leaks. Postoperatively, wound exploration and reclosures for CSF leakage were more likely in the craniectomy group (11 compared with 0%; p < 0.01). Multivariate analysis revealed that the only predictor of CSF leakage postoperatively was the type of surgery (that is, craniotomy compared with craniectomy; odds ratio 10.8; p = 0.03). CONCLUSIONS: Craniectomy was associated with postoperative CSF leaks, pseudomeningocele, increased wound reclosures, and thus prolonged hospital stays. In turn, CSF leakage was associated with infections of the CSF and wound. The authors propose mechanisms that may explain why CSF leakage is less likely if the bone flap is replaced.

Cerebrospinal Fluid↗