Perception of Undergraduate Dental Students Regarding Teaching Learning Methods in Oral Pathology.

Background Third year is considered crucial in undergraduate dental education as this is when students start to have clinical exposure and taught about various oral pathologies. Many a times, students fail to make proper clinical and pathological correlation. It is the responsibility of teacher to impart adequate knowledge to the students regarding a disease in most effective way. Understanding the students perception is an effective way of making new roadmaps for teaching. Objective To assess undergraduate dental student's perspectives regarding oral pathology along with the effectiveness of various teaching learning methods and assessment methods currently used by faculties of Department of Oral Pathology. Method This cross sectional study was conducted from June 2023 to July 2023 among 136 undergraduate dental students of Kathmandu University School of Medical Sciences by using the pretested questionnaire. Convenience sampling method was used. The data collected were entered into the Microsoft Excel Sheet and statistical analysis was done using Statistical Package for the Social Sciences version 20. Result A total of 136 students participated in the study. Among them, 46 (33.8) were from third year, 51 (37.5) were from fourth year and 39 (28.7) were from fifth year. Half of the students believed that oral pathology is an interesting subject. Most of students; 66 (48.5) participants strongly agreed that knowledge of oral pathology helps in clinical training. Except two students, all the participants said that integration of oral pathology teaching with clinical training will help in better understanding of diseases. More than half of the students 71 (52.2) agreed that lectures and demonstrations taken by faculties has stimulated interest in the subject. Most students 80 (58.8) believe that formative assessment serve the purpose of analyzing the cognitive skill. Sixty six (48.5) students agree that MCQs are an effective tool for analyzing cognitive skills. Conclusion The overall perception of undergraduate dental students regarding the oral pathology subject and the teaching learning method used by faculties is good. However, incorporation of case based learning, integration of oral pathology with other clinical subjects and taking regular feedback from students may be of great use in providing holistic and effective learning environment.

Ultrasound Guided Estimation of Skin to Subarachnoid Space Depth in Patients Scheduled for Elective Surgeries under Subarachnoid Block.

Background Subarachnoid block is one of the commonly used techniques of regional anesthesia and accurate placement of spinal needle is crucial. A conventional spinal needle may be too long for a lean patient or too short in obese patients leading to multiple attempts, inadvertent nerve injuries and patient discomfort. So a pre-procedural estimation of the skin to subarachnoid space depth may be beneficial. Objective To estimate the skin to subarachnoid space depth using ultrasound and correlate it with the length of spinal needle to be inserted during subarachnoid block. Method This was a prospective, observational study conducted at Bir Hospital, Kathmandu in patients undergoing elective surgeries under subarachnoid block. A pre-procedural ultrasound of lumbo-sacral spine using 2-5 Hz curvilinear probe was done to measure skin to subarachnoid space depth (SSD) at the level of L3-L4 interspace. Then under all aseptic precautions, subarachnoid block was performed and the length of spinal needle outside the skin was measured and that length was subtracted from the standard length of needle to get the inserted length of spinal needle. These two measurements were compared. Result In the fifty patients included in the study, ultrasound estimated skin to subarachnoid space depth was found to be 4.24 ± 0.48 cm and the inserted length of spinal needle was 4.24 ± 0.46 cm. A significant correlation r=0.96 (p < 0.05) was found between the two measurements in the study population. Conclusion Ultrasound estimated skin to subarachnoid depth in the study population was found to be 4.24 ± 0.48 cm which correlated with the inserted length of spinal needle. So, use of ultrasound can be very helpful in performing subarachnoid block.

COVID 19 Vaccine Breakthrough Infection among Health Care Workers.

Background Mass vaccination is considered the primary strategy for reducing the impact of COVID-19, and it has been implemented globally. Objective To study the extent of SARS-CoV-2 infection and breakthrough infection among the HCWs who were fully vaccinated for at least 14 days and investigated the relation between neutralizing antibody response and breakthrough infection. Method This study was a retrospective cohort study among health care workers at Dhulikhel Hospital Kathmandu University Hospital from December 2021 to October 2022. The interviews with semi structured questionnaire were conducted in person or over phone. Out of 1450 participants 137 fully vaccinated HCWs without breakthrough infection were randomly selected for the prospective serological cohort. Result Out of 1079 participants' majority (51.8%) were of age 25-34 years. Two thirds (66.7%) were females. More than half of participant (54.7%) had infection with SARS-CoV-2 at least once whereas more than one third people (35%) had reported SARS-CoV-2 infection 14 days after receiving full vaccination. Infection after vaccination had less moderate and sever/critical illness and less need for hospitalization as compared to infection before vaccination. Staffs who were directly involved in patient care had higher chance of breakthrough infection compared to those not involved directly in patient care. Those who had prior infection or booster dose had relatively higher antibody level and participants with low level of antibody had higher chance for breakthrough infection (35.3%) than participants with moderate to high level of antibody (11.9%). Conclusion Vaccinations significantly decreased severe diseases and the need for hospitalizations. Breakthrough infection was higher among the health care workers involved in direct patient care and with low level of antibody.

Self-confidence Level among Intern Dentists in Performing Endodontic Treatment Procedures in Nepal.

Background Endodontics is considered as one of the most difficult and stressful disciplines in dentistry. This might be due to the complex anatomical variations, recent advances in equipment, technology, materials and lack of self-confidence. Objective To determine the self-confidence level among the intern dentists in performing endodontic procedures from six different colleges of Kathmandu University, Nepal. Method A descriptive cross-sectional study was conducted among 145 intern dentists. The online questionnaire regarding confidence level (5 point Likert scale) in different endodontic procedures and difficulty level (easy, ok and difficult) with respect to teeth was distributed. For descriptive purpose, frequency and percentage for each response were calculated. Result Dental interns were confident in performing majority of the normal endodontic procedures, however, they showed less confidence in performing difficult steps like rubber dam application for anterior (74, 51%) and posterior tooth (91, 62.7%), use of electronic apex locator (89, 61.4%), using rotary files (114, 78.6%), management of flare-ups (86, 59.4%), assessment of quality of post-endodontic treatment (85, 58.5%), recall periods (75, 51.6%) and performing post and core (82, 56.6%). Likewise, upper first molars (84, 57.9%) and second molars (104, 71.7%) were found to be the most difficult teeth to treat. Conclusion It can be concluded that majority of the dental interns were confident in performing basic endodontic procedures, however, they were found to have low confidence in performing difficult steps. Further training and exposure should be incorporated to increase their confidence level.

Juvenile Generalized Myasthenia Gravis: Presented as Unilateral Blepharoptosis and Successfully Managed with Pulse Intravenous Methylprednisolone.

Myasthenia Gravis is a rare autoimmune disorder of childhood and this is rarer in South Asia. We present a pre-pubertal 7 year old female child of seropositive Generalized Juvenile Myasthenia Gravis. She presented with unilateral blepharoptosis and later generalized symptoms appeared. Ice-pack test, Neostigmine challenge test and acetylcholine receptor antibody test were positive. Serum muscle specific tyrosine kinase antibody test was normal. She did not have thymic abnormalities. She did not respond to high dose (26 mg/kg/day) of Pyridostigmine and oral Prednisolone (2 mg/kg/day), but was successfully treated with a combination of pulse intravenous Methylprednisolone (30 mg/kg once a month for 6 months) and daily doses of oral Prednisolone (2 mg/kg/day) along with Pyridostigmine without significant side effects. This combination can be considered a potential inexpensive treatment for Juvenile Myasthenia Gravis in a resource limited area where other immunosuppressive treatments such as intravenous immunoglobulin is expensive and unaffordable.

Pattern of Dental Problems among Patients Visiting a Dental Hospital during COVID-19 Pandemic.

Background Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Nepal is a part of this worldwide corona virus disease. In this critical situation, the patients have a sense of insecurity visiting dental hospital. Objective To assess the pattern of dental problems in patients visiting a dental college during COVID-19. Method A descriptive cross-sectional study was conducted in Dental Hospital of Kathmandu Medical College and Teaching Hospital from May to August 2020. The patients visiting the Dental hospital were assessed for dental problems. Data were analyzed in Statistical Package of Social Sciences version 20. Frequency and percentage for pattern of dental problems were calculated. Result Most of the patients of age group of 14 to 31 years 530 (36.53%) had dental problems during the survey period. Out of total patients having dental emergency, 739 (50.93%) were males and 712 (49.07%) were females. Majority 545 (37.56%) visited the dental hospital for endodontic consultation followed by emergency consultation for oral surgical procedures 298 (20.54%). Least consulted dental emergency condition was prosthodontic consultation 18 (1.24%). Conclusion The study findings showed that the major dental problems in patients causing emergency visit to dental hospital during COVID-19 pandemic period were dental pain and swelling requiring endodontic consultation and the least need felt is prosthodontic consultation.

Effect of Breastfeeding on Relieving Pain during Immunization in Infant.

Background Advantages due to immunization are numerous and cannot be avoided but at the same time pain inflicted on babies needs to be addressed when possible. Pain associated with immunization injections has often been overlooked when remedies are available. Objective To find out the effect of breastfeeding on relieving pain during immunization injection in infants. Method An experimental study was conducted at Immunization clinic of B.P. Koirala Institute of Health Sciences (BPKIHS). Total 124 subjects were divided randomly into two groups. Experimental subjects were allowed to breastfeed for 5-10 minutes before immunization while control group was immunized without breastfeeding. Interview Questionnaire was used to obtain demographic variables and measurements were obtained. Measures of pain was recorded using duration of cry and Modified Behavior Pain Scale, by Taddio et al. Data was analyzed by using SPSS 20.0 where variables were assessed with frequency tables, Pearson's Chi-Square test, independent t test and Mann Whitney U test. Result The mean pain score in experimental group was 7.10 and in control group 7.56 which was statistically significant (p=0.001). The median duration of cry was significantly shorter in experimental group i.e. 25 seconds (IQR: 20-30) than control group 42.5 seconds (IQR: 30-61.5) (p < 0.001). Conclusion Breastfeeding before immunization is effective in reducing pain in infants.

Feedback-based Self-improving CNN Algorithm for Breast Cancer Lymph Node Metastasis Detection in Real Clinical Environment.

Digital pathology can be thought of as a model composed of 3 main elements; classification algorithm, Graphical User Interface (GUI) and the pathologists. Currently there is only a one way interaction from the classification algorithm to the pathologist. This paper, proposes an additional backward path which is a new feedback-based method, aimed to improve the performance of the classification algorithms by utilizing the feedback of the pathologists. The GUI developed for this purpose, is aimed to be simple and adaptive to different classification algorithms. The method showed significant improvement in the classification performance of the applied Convolutional Neural Network (CNN) algorithm. The 25% quantile of the probability score of the predictions increased from 0.48 to 0.89 and the median of the data increased from 0.95 to 0.99.

Therapeutic Drug Monitoring of Antiepileptic Drugs at a Tertiary Care Hospital of Eastern Nepal.

Background Therapeutic drug monitoring (TDM) is the process of measuring drug level in body fluids. It is done to maintain plasma concentration of the drug under therapy within a specific target range for maximum therapeutic efficacy without unnecessary exposure to adverse effects. Objective This study aims to evaluate necessity of therapeutic drug monitoring in Phenytoin, Carbamazepine and Lamotrigine therapy among epileptic patients. Method A prospective, cross-sectional study was conducted for a period of one year at BP Koirala Institute of Health Sciences, Dharan, Nepal. After taking detailed history, blood samples were collected from epileptic patients on monotherapy with the selected drugs. Plasma levels of these drugs were analyzed using High Performance Liquid Chromatography technique (HPLC). Out of total 42 selected patients, 21 were tested for phenytoin, 17 for carbamazepine and four for lamotrigine. The result was categorized into therapeutic, sub-therapeutic and above-therapeutic groups based on reference range. Result Out of total 21 samples tested for phenytoin, 15(71.4%) had plasma drug level within therapeutic range, 5(23.8%) had within subtherapeutic range and 1(4.8%) had above therapeutic range. Analysis of carbamazepine plasma level showed 14(82.3%) at therapeutic level, 1(5.9%) at sub-therapeutic level and 2(11.8%) at above-therapeutic level. Lamotrigine testing in four samples showed 2(50% in) both within therapeutic range and above-therapeutic range. Conclusion Therapeutic drug monitoring of phenytoin, carbamazepine and lamotrigine showed variation in plasma level irrespective of the therapeutic dose. It is suggested that dose adjustment of antiepileptic drugs should be done after establishing 'individual therapeutic range' following regular plasma monitoring.

Clinicopathological Analysis of Oral Lesions - A hospital based retrospective study.

Background Proper diagnosis plays a key role that determines treatment and prognosis of the disease. To give appropriate clinical diagnosis, clinicians must be well aware of the presentation and demographic information of the lesion including the rare ones. Histopathology is still considered as gold standard in diagnostic pathology but final diagnosis becomes difficult unless detailed clinical and radiological descriptions are given. Hence an interdisciplinary approach is needed which requires correlation between both clinical and pathological details. Objective To analyze the clinicopathological details of all the oral lesions diagnosed in Dhulikhel hospital within the period of two years and to assess the concordance between clinical and histopathological diagnosis of these lesions. Method Laboratory record file of all the oral lesions diagnosed between January 2016 to December 2017 were retrieved from the department archives and the data were collected. The extracted data were analyzed using SPSS version 23.0. Result A total of 237 cases were analysed in the present study. Odontogenic cysts were the most common category followed by benign lesions. However considering the individual lesion, mucocele was the commonest lesion followed by squamous cell carcinoma. Total concordance between clinical and histopathologic diagnosis was found in 56.5% cases. The most clinicopathological agreement was seen for benign lesions followed by malignant lesions. Conclusion Mucocele and oral squamous cell carcinoma are the two most common lesions found among the patients visiting our hospital. The cases of oral squamous cell carcinoma are on a rise with each subsequent year. At present, though it is the second most common entity, it can be hypothesized that it may be higher up on the list. Therefore, oral healthcare awareness is paramount and this may be one of the best ways to reduce the oral cancer incidence rates and lowering the healthcare management burden.

Eosinophilic Granuloma of Mandible: A Diagnostic Challenge.

Eosinophilic Granuloma is the mildest and localized form of Langerhans Cell Histiocytosis and is characterized by clonal proliferation of Langerhans cells. It is a rare disease, accounting for less than 1% of all the osseous neoplasms. It has predilection for the axial skeleton and incidence in jaws is just 7.9%. It lacks pathognomonic clinical and radiographic trait and hence is difficult to make a correct diagnosis without histopathological and immunohistochemical examination. This report describes a case of Eosinophilic Granuloma of mandible in 30 years old male who presented with complain of unhealed extraction wound and was clinically diagnosed as chronic suppurative osteomyelitis. The final diagnosis of Eosinophilic Granuloma was made only after histopathological and immunohistochemical evaluations.

Computerized Axial Tomography Findings in Children with Afebrile Seizures: A Hospital Based Study at Eastern Nepal.

BACKGROUND: Computerized Tomography can be performed in resource limited areas where Magnetic Resonance Imaging is less practical. This study was conducted to find out the proportion of cases with abnormal CT scan and findings of CT scan in children with afebrile seizures in a resource limited area. METHODS: This prospective study was conducted from 1st July 2009 to 31st March 2014 in a university hospital of Nepal. Patients (1 month to 20 years of age) presenting with history of afebrile seizure were included. Neuroimaging was prescribed; children were treated and followed-up as per standard guideline. Data were analyzed using SPSS 16.0. RESULTS: There were 447 children with afebrile seizures included in the study. Male to female ratio was 1.6:1. Median age at presentation was 84 (interquartile range 36-144) months. CT scan was done in 321 (71.8%) cases. CT was abnormal in 143 cases, accounting for 32.0% out of total cases and 44.5% out of investigated cases. Among investigated cases, common CT findings were atrophy (13.4%), neurocysticercosis (12.1%), structural abnormalities (4.4%), stroke (3.7%), post-encephalitis changes (3.1%), nonspecific calcification (1.6%), tuberculoma (1.2%), tumor (0.9%), neurocutaneous syndromes (0.9%), hydrocephalus (0.9%) and other findings (2.2%). CONCLUSIONS: In a resource limited area CT scan is a valuable alternative tool in evaluating a child with afebrile seizure. Majority of these children have remote symptomatic seizures and the underlying brain pathologies can be well detected by CT scan.

Peripheral Cemento-Ossifying Fibroma.

Peripheral cemento-ossifying fibroma (PCOF), a relatively uncommon lesion, reactive in nature is seen as an overgrowth of the gingival tissues often leading to periodontal problems. It is a benign tumor with slow-growing potential commonly affecting the anterior maxilla whose pathogenesis till date is uncertain. It is usually challenging to diagnose peripheral cemento-ossifying fibroma based on clinical observation and examination, hence histopathological examination is mandatory to arrive at an accurate diagnosis. Recurrence of the lesion is common unless and until it is completely excised. We present the report of two cases of peripheral cemento-ossifying fibroma of our department, complaining of a mass in the gingiva of posterior maxilla and mandible.

Recurrence Risk of Febrile Seizures in Children.

BACKGROUND: Identifying children with febrile seizure who are at risk for recurrence is important so that special attention can be given to them. The objective of this study was to identify the risk factors for recurrence of febrile seizures in children. METHODS: This prospective hospital based study was conducted from July 2013 to August 2014 'among children of 6 months to 6 years of age at Bishweshwar Prasad Koirala Institute of Health Sciences (BPKIHS), Nepal. Children meeting the selection criteria were enrolled in study. Clinical, investigation, treatment and outcome parameters were analyzed. RESULTS: A total of 92 children with febrile seizure were enrolled in study. Males accounted for 70% and females 30%. Simple febrile seizure was present in 48% and complex febrile seizures were seen in 52%. Recurrence of seizure was seen in one third of cases. Loss of consciousness was most common post-ictal phenomenon followed by confusion and lethargy. Upper respiratory infection was the most common precipitating factor. Generalized Tonic Clonic Seizure was the most common seizure type present in 79% of cases. Significant risk factors for recurrence occurred in males (p=0.088), age less than 1 year (p=0.003). Most of the recurrence occurred within one year of first seizure. CONCLUSIONS: Febrile Seizure is common in males. Almost one third of children with febrile seizure are at risk for recurrence. The significant risk factors for recurrences are male gender and age <1year.

Clinico-epidemiological study of low birth weight newborns in the Eastern part of Nepal.

Low birth weight (LBW) remains an important cause of newborn morbidity and mortality. A hospital based prospective and descriptive study was conducted at Paediatric wards, Nursery, Neonatal intensive unit (NICU) and Post natal ward during period of June to October 2010 to note the clinico-epidemiological profile of Low Birth Weight (LBW) newborns. Incidence of the LBW babies in our hospital was 14.45%; more than four fifth (82.2%) baby's mothers were primigravida. Eighty two percent mothers had unbooked pregnancies. Twenty and half percent LBW babies were twins. The mean duration of hospital stay of the subject was 7.4 (± 5.5) days. The mean birth weight of LBW babies was 1648 (± 344) grams. Clinical sepsis, non physiological jaundice and hypoglycaemia were the three most common complications of LBW babies. Antibiotics, oxygen and phototherapy were the three commonest modes of therapy. Majority of children (82.0%) improved and were discharged. Birth weight and gestational age were significantly different between survivors and babies who expired. Primigravida and lesser antenatal visits were important risk factors for Low birth weight babies. Birth weight, gestational age, apnoea and mechanical ventilation were the predictors of outcome.

USG assisted and USG guided percutaneous renal biopsy at Nepal Medical College Teaching Hospital: a three and half years study.

A prospective study was carried out from 2009 to 2013 in the Department of Radiology and Imaging of Nepal Medical College and Teaching Hospital, Attarkhel, Jorpati, Kathmandu, Nepal, in which a total of 75 patients underwent percutaneous renal biopsy with a 16 or 18 gauge needles. This was done blindly by marking a site on the skin, or, whenever there was difficulty with the blind procedure, by direct real time USG guidance. In all cases, the marking in the skin was done by the radiologist and the biopsy was performed by the Nephrologist, with the aid of the radiologist in cases of real-time USG guided renal biopsy. This study was carried out to assess the safety and efficacy of the USG aided, and USG guided renal biopsy, to see for the types and severity of complications arising from renal biopsies to determine the optimal period of observation required after the procedure. All renal biopsies were performed after the patients were admitted to the hospital at least 1 day prior to the procedure. Coagulation profile was done in all patients prior to the procedure. All patients were kept under strict complete bed rest for 24 hours post procedure. The ages of the patients ranged between 14 years to 71 years, with 42 female and 33 male patients. A mean of 21.8 glomeruli was obtained in each specimen, with absent glomerular yield seen in only 3 patients. Minimal change disease was seen in 19 patients, being the most common histopathological diagnosis followed by a spectrum of others. The overall complication rate was 4% and all of these were self-limiting needing no other intervention, or management except for observation and bed rest. Late complications were not seen. Percutaneous renal biopsy with the help of USG is a safe and efficacious procedure with less chance of minor complications.

Stapled haemorrhoidectomy in the operative treatment of grade III and IV haemorrhoids.

Stapled haemorrhoidectomy (SH) is a minimally invasive intervention that uses a stapling device which avoids the need for wounds in the sensitive anal area and reduces the pain after surgery. This study was undertaken in Nepal Medical College Teaching Hospital from January 2010 to December 2012 to evaluate the efficacy of this modality of treatment among patients (32) who presented in the Surgery OPD with grade III and grade IV haemorrhoids. The results of SH were evaluated by the relief of symptoms, severity of post operative pain, and complications of SH. Twenty five (78.1%) patients had grade III and 7 (21.9%) presented with grade IV hemorrhoids. The most frequent presentation reported in our study was bleeding per rectum with perianal prolapse. Mean operating time was 40-60 minutes whereas mean hospital stay was 1.9 days. Urinary retention was the most common complication found in 12 (37.5%) patients in the immediate post operative period. SH is a safe, rapid, and convenient surgical remedy for grade III and grade IV hemorrhoids with low rate of complications, minimal postoperative pain, and shorter hospital stay.

Comparative study of sensitivity of rapid diagnostic (hexagon) test with calculated malarial parasitic density in peripheral blood.

BACKGROUND: Different diagnostic test kits are used for rapid diagnosis of malaria. Most are based on antigen detection (pLDH, Pan Aldolase, HRP-2). In context of Nepal the diagnostic reliability and sensitivity of these tests is unknown. Hexagon Malaria Combi™ is one of the most commonly used test kit in Nepal for rapid diagnosis of malaria. The aim of the present study is to evaluate the sensitivity of the Hexagon malaria Combi test in comparison with parasitic density by microscopy technique. METHODS: A Cross sectional prospective study was conducted in three districts of Nepal from September to November 2009. Blood samples were collected from the suspected cases of malaria. Thick and thin smear were prepared from all the samples and Giemsa stain was done. Simultaneously RDT (hexagon) for malaria was done. When RDT was found to be positive, blood was serially diluted in 6 tubes as 1:2, 1:4, 1:8, 1:16, 1:32 and 1:64. RDT was done on diluted blood till RDT test gave negative result. Parasitic density was calculated for undiluted and diluted blood samples and sensitivity of RDT in various parasitic densities was calculated. RESULTS: Hexagon malaria combi test is sensitive (86%) when malarial parasitic density is >500/µl. Sensitivity was found to be directly related to parasitic density. Its sensitivity is very low (2.9%) when parasitic density is less than 500/ µl. CONCLUSIONS: The sensitivity of rapid diagnostic test (hexagon Combi test detecting malarial pLDH antigen) is high only if the parasitic density is more than 500/µl.

Effects of thermal annealing on the structural and optical properties of carbon-implanted SiO2.

Amorphous carbon (a-C) nanoclusters were synthesized by the implantation of carbon ions (C-) into thermally grown silicon dioxide film (-500 nm thick) on a Si (100) wafer and processed by high temperature thermal annealing. The carbon ions were implanted with an energy of 70 keV at a fluence of 5 x 10(17) atoms/cm2. The implanted samples were annealed at 1100 degrees C for different time periods in a gas mixture of 96% Ar+4% H2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) were used to study the structural properties of both the as-implanted and annealed samples. HRTEM reveals the formation of nanostructures in the annealed samples. The Raman spectroscopy also confirms the formation of carbon nano-clusters in the samples annealed for 10 min, 30 min, 60 min and 90 min. No Raman features originating from the carbon-clusters are observed for the sample annealed further to 120 min, indicating a complete loss of implanted carbon from the SiO2 layer. The loss of the implanted carbon in the 120 min annealed sample from the SiO2 layer was also observed in the XPS depth profile measurements. Room temperature photoluminescence (PL) spectroscopy revealed visible emissions from the samples pointing to carbon ion induced defects as the origin of a broad 2.0-2.4 eV band, and the intrinsic defects in SiO2 as the possible origin of the -2.9 eV bands. In low temperature photoluminescence spectra, two sharp and intense photoluminescence lines at -3.31 eV and -3.34 eV appear for the samples annealed for 90 min and 120 min, whereas no such bands are observed in the samples annealed for 10 min, 30 min, and 60 min. The Si nano-clusters forming at the Si-SiO2 interface could be the origin of these intense peaks.

Anomalous formation of the circulus arteriosus and its clinico-anatomical significance.

Circulus arteriosus (Circle of Willis) is an anastomotic ring which unites the internal carotid and vertebrobasilar systems. It slows down the blood before it reaches the brain and helps in collateral circulation. Anatomic study reveals the variation in the pattern and calibre of vessels which make up the circulus arteriosus. The greatest variation in calibre occurs in the posterior communicating artery. The posterior cerebral artery is divided into three portions by the posterior communicating artery; these are- P1, P2, and P3. Three basic configurations of the posterior communicating artery has been described; foetal, transitional and adult. In foetal configuration: the diameter of the P1 segment of posterior cerebral artery is less than the diameter of posterior communicating artery so that the blood supply to the occipital lobes is mainly via the internal carotid arteries. Thirty five circulus arteriosus of the formalin embalmed brains were studied during the period of three years. Posterior cerebral and posterior communicating arteries were traced from their origins to terminations. It is revealed that in 8.6% of cases the formation of the circulus arteriosus was anomalous. The calibre of the pre communicating (P1) segment of posterior cerebral artery was smaller than the posterior communicating artery. It appeared that the posterior cerebral artery is the continuation of posterior communicating artery, thus the branch of the internal carotid artery. Anomalies of the formation of circulus arteriosus leads to stroke. The neurosurgical importance of this study lies during the exposure of the region for different purposes. Knowledge of the vascular variations will increase the success of the procedure.