Items tagged “anatomical variant”

The 5th metacarpal pit refers to the normal exaggeration of the pit-like depression in the head of fifth metacarpal 1.  Differential diagnosis It should not be mistaken for a boxer fracture (old or new) or an erosion.

An azygos lobe is a normal variant that develops when a laterally displaced azygos vein creates a deep pleural fissure into the apical segment of the right upper lobe during embryological development. It is not a true accessory lobe as it does not have its own bronchus or corresponding specific ...

Concha bullosa (plural: conchae bullosae) (also known as middle turbinate pneumatization) is a common finding and although associated with deviation of the nasal septum, it is usually of little clinical importance. Epidemiology Concha bullosa is a normal variant and is one of the most common v...

Os acromiale is an anatomical variant and represents an unfused accessory center of ossification of the acromion of the scapula. Epidemiology Os acromiale is relatively common, seen in ~8% (range 1-15%) of the population 1,2 and can be bilateral in 60% of individuals 5. Clinical presentation ...

A bifid median nerve is an uncommon anatomical variation in the forearm and has an increased association with a persistent median artery 4. Epidemiology It has an incidence of 9-19% 4. A persistent median artery is present in approximately half of those with a bifid median nerve 4. Gross anat...

Popliteal artery entrapment syndrome refers to symptomatic compression or occlusion of the popliteal artery due to a developmentally abnormal positioning of the popliteal artery in relation to its surrounding structures such as with the medial head of gastrocnemius or less commonly with popliteu...

The extensor digitorum brevis manus (EDBM) muscle is an accessory muscle in the hand and is a normal anatomical variant.  Summary origin: distal radius and posterior radiocarpal ligament insertion: extensor hood of 2nd or 3rd digits (variable) innervation: posterior interosseous nerve actio...

Anomalous pancreaticobiliary junction, also known as pancreaticobiliary maljunction, describes the abnormal junction of the pancreatic duct and common bile duct that occurs outside the duodenal wall to form a long common channel. Epidemiology The incidence varies from 1.5% to 3.2% 11. The esti...

Some ostiomeatal complex anatomical variations, which do not cause disease by themselves, can promote narrowing and even obstruction 1: concha bullosa ~10% (range 4-15%) - aerated middle turbinate intralamellar cell: air cell within vertical portion of the middle turbinate  oversized ethmoid ...

Accessory fissures of the lung usually occur at the borders of bronchopulmonary segments. They are common normal variants but are less commonly seen on imaging.  Some of the more common accessory fissure include 1: azygos fissure: most commonly seen accessory fissure inferior accessory...

The vertical fissure line commences in or near the costodiaphragmatic recess and heads superomedially towards the hilum and terminates before or at the horizontal fissure. More commonly occurs on the right and may indicate partial volume loss of the lower lobe 1.

The inferior accessory fissure of the lung, also known as Twining's line, divides the medial basal bronchopulmonary segment from the rest of the lower lobe 4. Epidemiology This accessory fissure is present in around 12% of people when examined with CT 3and is visible on 8% of PA chest x-rays 4...

Riedel lobe is a common anatomical variant of the liver to be aware of because it can simulate a mass. Its misidentification as a pathologic abdominal mass has led to surgery. Pathology can also occur within it (e.g. malignancy or even torsion) and cause atypical hepatic symptoms low in the pelv...

Anatomical variants represent the deviations from the accepted standard human anatomy as printed in the classic textbooks (e.g. Gray's Anatomy 1), and taught in universities, dissecting rooms and clinical practice. Terminology The term "normal anatomical variants" or just "normal variants" is ...

Anomalous systemic arterial supply to normal lung is an anatomical variant in which a portion of the lung (usually a basal segment) is supplied by a systemic vessel without a distinct pulmonary sequestration. Terminology It was traditionally (perhaps inappropriately since not a true sequestrat...

An absent azygos vein is a very uncommon variant in which the azygos vein fails to develop. In cases of agenesis of the azygos vein, the hemiazygos and accessory hemiazygos veins play an important role in venous drainage, accounting for drainage of both the right and left intercostal veins 1-3. ...

A non-recurrent laryngeal nerve is an uncommon anatomical variant in which the laryngeal nerve does not descend into and return from the thorax, instead directly entering the larynx from the cervical vagus nerve. Epidemiology Incidence is rare and varies by study but has been indicated to be a...

A thyrolingual trunk is an anatomical variant in which the superior thyroid artery and lingual artery share a common trunk 1. This is in contrast to the typical pattern of both vessels emerging independently from the external carotid artery. Other variations of origin include a linguofacial trun...

A linguofacial trunk is a rare variation of the anterior branches of the external carotid artery. The lingual artery and facial artery share a common trunk rather than branching independently from the external carotid artery 1. Unlike the thyrolingual or thyrolinguofacial variations in which the...

A thyrolinguofacial trunk is a very rare pattern of branching of the anterior branches of the external carotid artery. Rather than the facial artery, lingual artery, and superior thyroid artery having their own distinct origins, all three vessels originate from a common trunk of the external car...