Variations in Division of Sciatic Nerve and its Clinical Relevance: A Cadaveric Study

Introduction:The sciatic nerve emerges through the greater sciatic foramen, leaves pelvis and enters into gluteal region by passing below piriformis as a single nerve encompassed by a single epineural sheath. It descends along back of thigh and divides into tibial nerve and common peroneal nerve, usually at superior angle of popliteal fossa. Understanding of variations in the levels of division of sciatic nerve is important for the management of non- discogenic sciatica, posterior hip operations, failed sciatic nerve block. Objective: To study the variations in division of sciatic nerve and to define the level of its exit.Subjects and Methods:Seventeen cadavers (34 limbs) fixed in formalin were dissected and studied during routine dissection in department of Anatomy, Mysore Medical College and level of division of sciatic nerve were noted.Results:Out of 34 limbs, 5 cases (14.7%) were dividing at gluteal region, 2 cases (5.8%) at mid-thigh and 27 cases (79.4%) exited pelvis as a whole nerve and divided at superior angle of popliteal fossa. Type G was most common variation.Conclusion:The exit and level of division of sciatic nerve is important for surgeons as there is surgical maneuvering in this region during posterior hip operations and to avoid iatrogenic nerve injury during deep intramuscular injections in gluteal region.

Morphometric features of asterion in adult human skulls.

Background: Asterion is the meeting point of temporal, occipital and parietal bones on the posterolateral surface of skull and surgically an important point of reference for approaching the posterior cranial fossa structures. However surgeons have been skeptical about its reliability due to population based differences in its morphology, distance with other external landmarks and also to sigmoid and transverse sinuses. Methods: In this study 50 (27 male & 23 female) adult skulls were investigated to determine the type of asterion, its distance from important bony landmarks and also the nearby venous sinuses were measured. Results: Our study revealed that type II (absence of sutural bones) was commoner than type I (presence of sutural bones) asterion. The asterion was 4.82 ± 0.58 cm from tip of the mastoid process on the right side and 4.70 ± 0.70 cm on the left. It was greater in males than in females, p value being statistically significant (P = 0.00 & P = 0.02 for right & left sides respectively). The distance of asterion from supramastoid crest was 4.22 ± 0.73 cm on the right and 4.23+/-0.58 cm on the left. The distance in males was more than in females. The P value 0.00 was statistically significant on the right side. Regarding the position of the asterion in relation to transverse sinus, it was on the transverse sinus in 62% cases, below it in 32% and above in 6%. Conclusions: The data obtained shows that the asterion is located either at the level or below the level of the transverse sinus in majority of the cases. This information is useful to neurosurgeons to reduce the risk during posterior cranial fossa surgeries. This work will also be useful to anthropologists, forensic science experts for determination of sex of the skull along with other parameters.

Morphometric study on posterior papillary muscles of human tricuspid valve.

Background: Aim of the present study was to observe the measurements of posterior papillary muscles present in tricuspid valve of human heart. Measurements of posterior papillary muscles in tricuspid valve gains utmost importance in cardiac surgeries because they are the causes of myocardial infarction in recent times because of its variations and detection of these causes by advent in modern technologies which will help in treatment of tricuspid valve diseases. Material and methods: This study was carried out on 96 normal formalin fixed human heart specimens. Dissection was performed according to standard techniques. Posterior papillary muscles were observed and length, width and thickness of each muscle were measured and documented. Results: In the present study, numbers of posterior papillary muscles were present with a frequency of 0-7, with most common appearance of 2 muscles in 38 hearts (39.6%) and least common incidence of 0 muscles in 1 heart (1%). Posterior papillary muscles were present in 95 hearts, with maximum number of 7 muscles in 1 heart (1%) and minimum number of 1 muscle in 27 hearts (28.1%). In measurements of papillary muscles, posterior papillary muscle mean height was 1.05±0.37 cm, mean width was 0.63±0.17 cm and mean thickness was 0.5±0.11 cm respectively. Conclusion: This study serves to understand the morphometry of posterior papillary muscles better and can help in various surgical procedures and cardiac treatment done on tricuspid valve.

Situs inversus.

Situs inversus is a rare condition with a genetic predisposition, where in organs are transposed from their normal location to the opposite side of the body with an incidence of 1 in 10000 live births. If Situs Inversus is associated with other congenital anomalies the survival rate is low. So prenatal diagnosis is essential to detect any associated anomalies. During routine fetal autopsies conducted in the department of anatomy, Mysore medical college, Mysore, a rare interesting case of still born baby with gestational age of 20 weeks was observed. Autopsy findings of external examination revealed kyphosis in thoracic region. Thoracotomy revealed heart on the right side (dextrocardia). Laparotomy revealed that the left lobe of liver was bigger than the right. The gall bladder was present on the visceral surface of the left lobe of liver, stomach was on right side, duodenum on left side, pancreas and spleen were on the right side. There was agenesis of right kidney, right ureter and both suprarenal glands. All the above findings correlate with the condition situs inversus. Situs inversus is a rare condition with a genetic predisposition, it’s etiology lies in the mutation of chromosome no 12, which is critical for recognition of right sidedness.1,2 Even though there is transposition of organs in situs inversus, the survival rate is good but if situs inversus is associated with other congenital anomalies the survival rate is low. So prenatal diagnosis is essential to detect any associated anomalies to bring down mortality rate.

Morphological variations of the thyroid gland.

Background: The knowledge of various morphological & developmental anomalies of thyroid gland will help the surgeons in better planning of safe & effective surgery. Considering these facts we studied the variations of thyroid gland. Methods: The material for the present study was collected from the department of forensic medicine, MMC & RI, Mysore, which includes 56 male and 33 female adult postmortem cadavers aged between 18 to 80 years. A dissection was carried out to expose thyroid glands & variations were observed in the morphology of thyroid gland. Results: 1) 9% of specimens had agenesis of isthmus. 2) 46% of specimens had pyramidal lobe. 3) 41% of specimens had levator glanduli thyroidae. 4) 2.24 % of specimens had accessory thyroid tissue. Conclusion: This study highlights the various morphological anomalies of the thyroid gland which forms cornerstone to safe & effective surgery.

Bilateral high division of sciatic nerve.

Sciatic nerve is the thickest nerve in the body formed by the sacral plexus from L4 to S3 in the lesser pelvis. It emerges through the greater sciatic foramen below the piriformis and enter the gluteal region. Then the nerve passes on the back of the thigh and at the level of superior angle of popliteal fossa it terminates by dividing into tibial and common peroneal nerve. The knowledge of anatomical variations in the division of nerve is important for various surgical and anaesthetic procedures. During routine dissection in the department of anatomy, Mysore Medical College & Research Institute, Mysore, a rare bilateral high division of sciatic nerve was observed in a female cadaver aged about 40 years. In the present case there was bilateral high division of sciatic nerve. The nerve was seen dividing into two branches before it emerges through the greater sciatic foramen. The tibial nerve was entering the gluteal region below the piriformis muscle and common peroneal nerve was entering by piercing the piriformis. The knowledge of this variation is important as the nerve may get compressed with surrounding anatomical structures resulting in non discogenic sciatica. The awareness of variations is important for surgeons during various procedures like fracture, posterior dislocation of hip joint and hip joint replacement. The anatomical variations are important during deep intramuscular injections in gluteal region and also for anaesthetists during sciatic nerve block.

Origin of accessory left hepatic artery from left gastric artery.

Liver is supplied by the branches of celiac trunk. Common hepatic artery which is a branch of celiac trunk continues as proper hepatic artery after giving gastroduodenal artery. Proper hepatic artery enters the liver at Porta hepatis after diving into right and left hepatic artery. The knowledge of branching patterns of arteries and their variations is important in various surgical and radiological procedures. During routine dissection conducted in the Department of Anatomy, MMC&RI, Mysore, an accessory left hepatic artery was seen arising from left gastric artery in an elderly male cadaver aged around 60 years. An accessory left hepatic artery was arising from left gastric artery and was entering the left lobe of liver. In less than 1% of cases, the accessory left hepatic artery supplies the part of left lobe of liver or whole liver. Knowledge of anomalous origin of left hepatic artery is important for successful liver transplant surgeries, hepatobiliary operations, gastrectomies, hiatal surgery for gastro esophageal reflex, bariatric surgeries and in selective arterial chemotherapy for liver cancers. Ligation or laceration of this artery during surgeries causes fatal ischemic necrosis of left lobe of liver.

Persistent Median Artery In the Carpal Tunnel.

Introduction: Persistent median artery originates from the anterior interosseous artery in proximal one-third of the forearm and accompanies median nerve. Median artery may regress in the forearm or enter palm through the carpal tunnel deep to flexor retinaculum of wrist and supply palm by anastomosing with the superficial palmar arch. Objective: In present study the objective was to study presence of persistent median artery accompanying median nerve and its termination Materials and Methods: The study included 50 human cadaver upper limb specimens at the Department of Anatomy, Mysore Medical College & Research Institute, Mysore during 2011-13. These specimens fixed in 10% formalin were finely dissected and persistent median artery was traced from origin to termination. Results: Out of 50 human cadaver specimens, persistent median artery was present in 4 specimens (8%). All the 4 median arteries originated from anterior interosseous artery and were of palmar type which reached palm. Out of 4 median arteries, 3 median arteries (6%) took part in completion of superficial palmar arch, supplying the distal aspect of palm and 1 median artery (2%) directly supplied radial two and half fingers without forming arch. Conclusion: Knowledge of unusual variations helps in proper treatment of disorders of the median nerve. Presence of persistent median artery usually will be asymptomatic but may cause symptoms of carpal tunnel syndrome or pronator teres syndrome when subjected to compression. Rarely this artery can be taken for reconstruction.

Prevalence of anatomical variations of cystic artery in South Indian cadavers.

Background: The knowledge of variations in the origin and course of cystic artery is important for the surgeons as uncontrolled bleeding from the cystic artery and its branches can be fatal during cholecystectomy. Intra operative bleeding can result in an increase in the risk of intra operative injury to vital vascular and biliary structures. Keeping in view the clinical significance and applied importance of the cystic artery anatomy and to add some more knowledge to the existing ones, the present study was undertaken, to know in detail the level of origin, length, and variations in the course and relation of the cystic artery. Methods: The present study was performed on 100 human liver specimens with intact gallbladder and extrahepatic duct system, obtained after dissection from the cadavers in the Department of Anatomy and from post-mortem cases from the Department of Forensic Medicine, Mysore Medical College and Research Institute, Mysore, over a period of 18 months. Results: Most common source of origin of the cystic artery was the right hepatic artery in 92 cases (92%) followed by aberrant right hepatic artery in 4 cases (4%) and the least common sources observed were the left hepatic artery in 1 case (1%) and the gastroduodenal artery in 1 case (1%).Mean length of the cystic artery was 17.6 mm and ranged between 3.7 mm to 42 mm. Out of the 100 dissected specimens, in 65 (65%) the cystic artery was found inside the Calot’s triangle and in 35 (35%) outside the triangle. Conclusion: This study provides details of the normal as well as the variant anatomy of the cystic artery, knowledge of which is very essential for the surgeons to minimize the risk of injury to the blood vessels and the biliary apparatus during cholecystectomy.

Congenital malformations in multiple births.

Objective: The present study was done to know and compare the incidence of congenital malformations in singleton and multiple births in our hospital & compare with other studies. Methods: A retrospective study done by collecting the data from parturition register from Jan 2008 to Dec 2011 (4yrs) from Cheluvamba Hospital attached to Mysore Medical College and Research Institute. Total number of the live births, still births, and abortions> 20 wks were collected. Details of multiple births such as maternal age, gestational age, sex & birth weight of the babies, U/S reports and congenital anomalies (CA) were noted. Results: The total number of singleton births were 48700 and number of babies who had congenital malformations were 235 (48.25/10,000 births).Total number of multiple births were 579 including 10 triplets and number of babies who had CA were 11 (189.98/10,000 births, P<0.0001). In the present study sex of the babies were noted in all multiple births and zygosity could not be recorded. Among 579 multiple births 404 were of the Same Sex (SS) and 165 were of Opposite Sex (OS) in twins and 6 were of the same sex and 4 were of opposite sex in triplets. According to Weinberg formula 50% of same sex (SS) twins are monozygotic and 50% are dizygotic twins. Among the 11 babies with CA, 4 monozygotic twins had anomalies related to twinning such as Acardia with TRAP sequence (3 twins), and Thoracophagus (1 twin).5 babies had CNS anomalies, 1 with cystic hygroma, 1 baby with multiple system affected. Conclusion: The incidence of birth defects is more in multiple births and especially in monozygotic twins. In the present days increase in twinning rate due to advanced maternal age, hereditary factors and use of ovulation inducing drugs, which results in premature and low birth wt babies associated with poor lung maturity.