Absent Posterior Belly of Digastric Muscle.

OBJECTIVE: Report a unique case of absent posterior belly of digastric muscle, with a literature review and discussion of its clinical importance. METHODS: Present a case report and review the current literature including PUBMED search terms; "absent posterior digastric", "digastric muscle", "posterior belly". RESULTS: While there were multiple reports of accessory anterior and posterior bellies and absence of anterior belly, there is a paucity of literature on absence of posterior belly of digastric muscle. CONCLUSION: To our knowledge, this is the first report of an absent posterior belly of the digastric muscle. The posterior belly of the digastric muscle is an important landmark in neck dissection, and its absence makes knowledge of other anatomic landmarks critically important. Laryngoscope, 131:1501-1502, 2021.

Anomalies of the right vertebral vein increasing the difficulty of lymph-node dissection along the right recurrent laryngeal nerve: a single-institution, retrospective study.

BACKGROUND: Radical lymph-node dissection along the recurrent laryngeal nerves (RLN) improves the prognosis of patients with esophageal cancer. The RLN is a landmark for achieving adequate lymph-node dissection. However, the right RLN is sometimes covered by the right vertebral veins (VVs), making it undetectable. We investigated the relationship between this anomaly of the right VVs and the challenges of performing lymphadenectomy along the right RLN. METHODS: Patients with esophageal cancer, who underwent thoracoscopic esophagectomy with radical lymph-node dissection, were registered. The patterns of the right VVs were evaluated by preoperative computed tomography. The time required for identifying the right RLN or completing the lymphadenectomy was determined by reviewing surgical videos. RESULTS: In total, 178 patients were enrolled. Eighty patients (45%) had right VVs passing dorsal to the right subclavian artery (Dorsal group). More time was required to detect the right RLN in these cases (11 vs 9.5 min for the other cases, p = 0.034). In the Dorsal group, there were 15 patients who had specific VV patterns: The right VV converged on the lower portion of the right brachiocephalic vein (BCV), or passed through to the more medial side of the mediastinum. These patients required more time for detecting the right RLN (25 vs 9 min, p < 0.0001) and for completing the lymphadenectomy (41 vs 32 min, p = 0.048) than the other cases. CONCLUSION: The right VVs behind the subclavian artery, joining the lower part of the BCV or passing through the medial side, made it difficult to identify the right RLN and complete the lymphadenectomy.

Surgical review of the anatomical variations of the internal jugular vein: an update for head and neck surgeons.

BACKGROUND: The internal jugular vein is one of the major vessels of the neck. The anatomy of this vessel is considered to be relatively stable. It is an important landmark for head and neck surgeons as well as the anaesthetists for both diagnostic and therapeutic purposes. METHODS: We present two case reports of the posterior tributary of the internal jugular vein and review the surgical literature regarding anatomical variations of the vein. FINDINGS: A total of 1197 patients from 27 published papers were included in this review. Of these patients, 99.6% had neck surgery and the rest were cadaveric dissections. Anatomical variations of the internal jugular vein were found in 2% of the patient cohort (n = 40). The majority of these patients had either bifurcation or fenestration of the vein. The posterior tributary of the internal jugular vein is unusual and is scarcely reported in the literature (three cases). Knowledge of variations in the anatomy of the internal jugular vein assists surgeons in avoiding complications during neck surgery and preventing morbidity. Two rare cases of posterior branching of the internal jugular vein and experience of other surgeons are demonstrated in this extensive review.

Five mental foramina in the same mandible: CBCT findings of an unusual anatomical variant.

The mental foramen is an important anatomic landmark located on the buccal aspect of the mandible, typically near the apex of the second premolar. Mental foramina exhibit many anatomical variations, including differences in size, shape, position, and number. The most frequent type of variation in number is the presence of double mental foramen, which has a reported incidence ranging from 1.4 to 12.5%. The incidence of triple mental foramen ranges from 0.7 to 1.2%. The frequency of accessory mental foramina varies among ethnic groups, with a low incidence in white Caucasian populations. At present, cone beam computed tomography (CBCT) is the diagnostic tool of choice for examining the maxillofacial region, and the high spatial resolution of CBCT allows accurate three-dimensional analysis of mental foramen variations. The present report describes an unusual case of five mental foramina in a 24-year-old white European male diagnosed by CBCT.

Anatomic Variations of the Floor of the Third Ventricle: An Endoscopic Study.

OBJECTIVE: Anatomical variations of the floor of the third ventricle are common in hydrocephalic patients and can significantly affect outcomes of endoscopic third ventriculostomy (ETV). We sought to categorize variations in third ventricle anatomy and to discuss the implications of these variations for ETV. METHODS: Intraoperative videos and pictures of 50 patients who underwent ETV between April 2001 and August 2010 were reviewed. Twenty-seven patients with clearly demonstrable third ventricular floors that satisfied our criteria were selected for the study. RESULTS: Images of variations were organized into the following categories: 1) thinned floor, 2) thickened floor, 3) partially effaced floor, 4) ballooning/herniating floor, 5) small prepontine interval, 6) narrowed third ventricle, and 7) other significant anomalies. CONCLUSIONS: The third ventricle is a common site for anatomical variations in hydrocephalic patients. A good knowledge of these variations is essential before performing ETV, because they have the potential to increase operative risk.

Descriptive study of the bifid mandibular canals and retromolar foramina: cone beam CT vs panoramic radiography.

OBJECTIVES: To examine the presence and morphologic characteristics of bifid mandibular canals (BMCs) and retromolar foramens (RFs) using cone beam CT (CBCT) and to determine their visualization on panoramic radiographs (PANs). METHODS: A sample of 225 CBCT examinations was analysed for the presence of BMCs, as well as length, height, diameter and angle. The diameter of the RF was also determined. Subsequently, corresponding PANs were analysed to determine whether the BMCs and RFs were visible or not. RESULTS: The BMCs were observed on CBCT in 83 out of the 225 patients (36.8%). With respect to gender, statistically significant differences were found in the number of BMCs. There were also significant differences in anatomical characteristics of the types of BMCs. Only 37.8% of the BMCs and 32.5% of the RFs identified on CBCT were also visible on PANs. The diameter had a significant effect on the capability of PANs to visualize BMCs and RFs (B = 0.791, p = 0.035; B = 1.900, p = 0.017, respectively). CONCLUSIONS: PANs are unable to sufficiently identify BMCs and RFs. The diameter of these anatomical landmarks represents a relevant factor for visualization on PANs. Pre-operative images using only PANs may lead to underestimation of the presence of BMCs and to surgical complications and anaesthetic failures, which could have been avoided. For true determination of BMCs, a CBCT device should be considered better than a PAN.