List of anatomical variations

This article provides a comprehensive list of anatomical variations, which are naturally occurring differences in human morphology. These variations are not considered defects or abnormalities but rather normal deviations that do not inherently indicate pathology. The frequencies in the tables below are mostly derived from meta-analyses. They are reported as percentage with 95% confidence intervals.

Head and neck

Skeletal variations

Name	Other Names	Description	Frequency
Accessory maxillary ostium		see Maxillary sinus
Arcuate foramen			9.1% (8.2%—10.1%)^[1]
Arcus praebasiocipitalis
Basilar tubercle of clivus			9.8%^[2]
Canalis basilaris medianus
Clivus bony canal
Collateral eminence
Condylus tertius
Craniopharyngeal canal
Foramen tympanicum
Fossa navicularis magna
Haller cell		see Ethmoid Sinus
Interparietal bone	Os Interparietale, Inca bone
Innominate canal of Arnold
Intermediate condylar canal
Os odontoideum			0.21%, (0.00%—0.72%)^[3]
Ossiculum terminale (of dens)	Bergmann's ossicle
Ossified petrosphenoid ligament
Sphenoethmoidal air cell	Onodi cell	see Sphenoid sinus
Stafne bone cavity			0.17% (0.14%—0.21%)^[4]
Thyroid foramen		see Thyroid cartilage	24.5% (19.2—29.8%)^[5]
Transverse basilar fissure	Saucer's fissure	see Clivus
Tubercle at the anterior rim of foramen magnum
Wormian bones	Sutural bones

Muscular variations

Name	Other Names	Description	Frequency
Accessory slip of levator palpebrae superioris
Accessory belly of Digastric muscle
Atlantomastoid muscle^[6]
Cleidoatlanticus muscle
Cleidocervical muscle
Cleidofascialis muscle
Cleidohyoideus muscle
Cleidomastoideus muscle
Cleidooccipitalis cervicalis muscle
Cricocorniculate muscle
Cricohyoid muscle		variation of thyrohyoid
Levator claviculae muscle
Levator glandulae thyroidea		levator muscle of thyroid gland
Pterygoideus proprius muscle
Sternoclavicularis anticus muscle
Styloauricularis muscle
Transversus nuchae muscle

Vascular variations

Name	Other Names	Description	Frequency
Persistent primitive olfactory artery
Artery of Percheron
Stapedial artery
Thyroid ima artery			3.8% (0.027%—0.049%)^[7]
Fourth thyroid vein	Fourth thyroid vein of Kocher	see Inferior thyroid veins
Falcine sinus
Hypoglossal artery
Persistent left superior vena cava
Trigeminal artery

Nervous variations

Name	Other Names	Description	Frequency
Aberrant facial nerve course
Accessory hypoglossal nerve
Trigeminal nerve duplication

Other variations

Name	Other Names	Description
Anisocoria
Crease of the upper eyelid		Single or Double eyelid
Empty sella turcica
Epicanthic fold
Darwin's tubercle
Diagonal earlobe crease
Preauricular sinus
Zuckerkandl's tubercle	Pyramidal lobe of thyroid gland

Vertebral column

Skeletal variations

Name	Other Names	Description	Frequency
Atlanto-occipital fusion		see Atlanto-occipital joint	0.64% (0.00%–1.00 %)^[8]
Atlas arch defect	Ossification anomalies of the atlas
Block vertebrae
Butterfly vertebrae
Cervical ribs
Coccygeal ribs
Diastematomyelia	Split cord malformation
Lumbosacral transitional vertebrae
Oppenheimer's ossicle
Sagittal cleft vertebrae
Spondylolisthesis
Spondylolysis
Sprengel's deformity	high scapula, scapular hypoplasia

Thorax

Skeletal variations


Name	Other names	Description	Frequency
Bifid rib
Bifid xiphoid process		see Xiphoid process
Episternal ossicles
Manubriosternal fusion		see Sternum
Sternal cleft
Sternal foramen
Sternoxiphoidal fusion
Xiphoid foramen

Muscular variations

Name	Other names	Description	Frequency
Sternalis muscle	Rectus Thoracis
Costocoracoideus muscle

Other variations

Name	Other names	Description	Frequency
Azygos lobe of the lung
Cardiac bronchus		see Bronchus
Horseshoe lung
Supernumerary lung fissures
Supernumerary nipple
Tracheal bronchus		see Bronchus

Upper limb

Skeletal variations

Name	Other names	Description	Frequency
Bifurcated clavicle
Bipartite capitate
Coracoclavicular joint
Carpal boss
Carpal coalition
Os acromiale		see Acromion
Scapular foramina and tunnels
Supracondylar process of the humerus

Muscular variations

Name	Other names	Description
Accessory subscapularis muscle
Axillary arch muscle
Chondroepitrochlearis muscle		see Pectoralis major
Coracocapsularis muscle
Costodeltoideus muscle
Epitrochleoanconeus muscle	Anconeus epitrochlearis
Extensor carpi radialis tertius muscle	Extensor carpi radialis accessorius
Extensor digitorum brevis manus muscle
Extensor indicis et medii communis muscle
Extensor medii proprius muscle
Extensor pollicis et indicis communis muscle
Flexor carpi radialis profundus muscle
Linburg-Comstock variation		Tendinous conjunction of the Flexor Pollucis Longus and Flexor Digitorum Profundus
Palmaris profundus muscle
Pisiuncinatus muscle	Pisohamate
Sternochondrocoracoideus muscle
Sternohumeralis muscle
Subclavius posticus	Chondroscapularis
Subscapularis minor muscle
Ulnaris quinti muscle
Tensor semivaginae articulations humeroscapularis muscle
Thoracobrachialis muscle^[9]

Vascular variations

Name	Other names	Description	Frequency
Alar thoracic artery
Median artery
Superficial ulnar artery
Variation of the basilic vein

Nervous variations


Name	Other names	Description	Frequency
Bifid median nerve		see Median nerve
Berrettini anastomosis
Froment-Rauber nerve
Martin-Gruber anastomosis
Nerve of McKenzie
Riché-Cannieu anastomosis

Other variations

Name	Other names	Description	Frequency
Accessory nail of the fifth toe
Osborne's ligament
Struthers' ligament

Lower limb

Skeletal variations

Name	Other names	Description	Frequency
Accessory navicula
Calcaneonavicular coalition
Cyamella		Sesamoid in the Popliteus muscle tendon.
Fabella		Sesamoid bone in the lateral head of the Gastrocnemius muscle.
Femoral anteversion/retroversion
Os tibiale externum
Os trigonum
Talocalcaneal coalition
Talus accessorius

Muscular variations

Name	Other names	Description
Accessory popliteus muscle
Accessory soleus muscle
Adductor minimus muscle
Fibularis quartus muscle	Peroneus quartus
Gastrocnemius tertius muscle		see Gastrocnemius muscle
Gluteoperinealis muscle
Gluteus quartus muscle
fibulocalcaneus internus muscle	Peroneocalcaneus internus
Popliteus biceps muscle
Tensor fasciae suralis muscle

Vascular variations

Name	Other names	Description	Frequency
Corona Mortis		see Obturator artery

Abdomen

Muscular variations

Name	Other names	Description	Frequency
Interfoveolar muscle
Pubotransversalis muscle
Saphenous muscle

Vascular variations

Name	Other names	Description	Frequency
Arc of Bühler	Bühler's anastomotic artery
Marginal artery of the colon	Marginal artery of Drummond
Third mesenteric artery

Other variations


Name	Other names	Description	Frequency
Accessory spleen
Accessory pancreatic duct
Agenesis of vermiform appendix		see Appendix (anatomy)
Annular pancreas
Bifid pancreas tail
Colon duplication
Double common bile duct
Gastropancreatic ligament
Pancreas divisum

Pelvis

Vascular variations

Name	Other names	Description	Frequency
Uterine artery anastomoses variations

Other variations

Name	Other names	Description	Frequency
Bladder exstrophy
Hirsuties coronae glandis
Horseshoe kidney (Ren arcuatus)
Renal artery anomalies
Splenogonadal fusion
Supernumerary ovaries

References

↑ Pękala, Przemysław A.; Henry, Brandon M.; Pękala, Jakub R.; Hsieh, Wan Chin; Vikse, Jens; Sanna, Beatrice; Walocha, Jerzy A.; Tubbs, R. Shane; Tomaszewski, Krzysztof A. (2017). "Prevalence of foramen arcuale and its clinical significance: a meta-analysis of 55,985 subjects". Journal of Neurosurgery Spine. 27 (3): 276–290. doi:10.3171/2017.1.SPINE161092. ISSN 1547-5646. PMID 28621616.
↑ Tangrodchanapong, Taweesak; Yurasakpong, Laphatrada; Suwannakhan, Athikhun; Chaiyamoon, Arada; Iwanaga, Joe; Tubbs, R. Shane (2023). "Basilar tubercles and eminences of the clivus: Novel anatomical entities". Annals of Anatomy = Anatomischer Anzeiger: Official Organ of the Anatomische Gesellschaft. 250 152133. doi:10.1016/j.aanat.2023.152133. ISSN 1618-0402. PMID 37460045.
↑ Klepinowski, Tomasz; Osiowski, Aleksander; Grzyb, Weronika; Esposito, Giuseppe; Osiowski, Maksymilian; Klepinowska, Marta; Taterra, Dominik; Sagan, Leszek (2026-01-08). "Prevalence of os odontoideum: a systematic review, meta-analysis and meta-regression with implications for vertebral artery and osseous anomalies". Neurosurgical Review. 49 (1): 112. doi:10.1007/s10143-025-04042-7. ISSN 1437-2320. PMC 12783242. PMID 41504791.
↑ Chaweeborisuit, Phanthip; Yurasakpong, Laphatrada; Kruepunga, Nutmethee; Tubbs, R. Shane; Chaiyamoon, Arada; Suwannakhan, Athikhun (2023). "The prevalence of Stafne bone cavity: A meta-analysis of 355,890 individuals". Journal of Dental Sciences. 18 (2): 594–603. doi:10.1016/j.jds.2022.08.022. ISSN 2213-8862. PMC 10068378. PMID 37021232.
↑ Srichaphan, Narathip; Yurasakpong, Laphatrada; Taradolpisut, Napawan; Senarai, Thanyaporn; Kruepunga, Nutmethee; Suwannakhan, Athikhun (2024). "The thyroid foramen: a systematic review and meta-analysis". Surgical and Radiologic Anatomy. 46 (10): 1673–1681. doi:10.1007/s00276-024-03470-2. ISSN 1279-8517. PMID 39191992.
↑ Lee, Rebecca; Pang, Stephen C.; Borman, William H.; Herrin, Sean O.; Bale, Logan S. W. (2022-10-01). "A prevalence study of the atlantomastoid muscle". Surgical and Radiologic Anatomy. 44 (10): 1349–1353. doi:10.1007/s00276-022-03022-6. ISSN 1279-8517. PMID 36155834.
↑ Yurasakpong, Laphatrada; Nantasenamat, Chanin; Janta, Sirorat; Eiamratchanee, Pinthusorn; Coey, James; Chaiyamoon, Arada; Kruepunga, Nutmethee; Senarai, Thanyaporn; Langer, Martin Franz; Meemon, Krai; Suwannakhan, Athikhun (2022). "The decreasing prevalence of the thyroid ima artery: A systematic review and machine learning assisted meta-analysis". Annals of Anatomy. 239 151803. doi:10.1016/j.aanat.2021.151803. ISSN 1618-0402. PMID 34265384.
↑ Bruna-Mejias, Alejandro; Salazar-Ferrari, Martina; Silva-Garay, Antonia; Chacon Valdebenito, Ignacia Belen; Ortiz -Ahumada, Cynthia; Trujillo-Riveros, Martin; Loaiza-Giraldo, Jessica Paola; Nova- Baeza, Pablo; Orellana- Donoso, Mathias; Santana- Machuca, Andres; Cifuentes-Suazo, Gloria; Oyanedel-Amaro, Gustavo; Paton, Glen; Nalla, Shahed; Valenzuela-Fuenzalida, Juan José (2026-06-01). "Occipitalization of the atlas: prevalence, functional and anatomical considerations. A systematic review and meta-analysis". Translational Research in Anatomy. 43 100465. doi:10.1016/j.tria.2026.100465. hdl:10550/122403. ISSN 2214-854X.
↑ Zielinska, Nicol; Karauda, Piotr; Węgiel, Andrzej; Szewczyk, Bartłomiej; Olewnik, Łukasz (2023-11-01). "A very rare case of a thoracobrachialis muscle". Surgical and Radiologic Anatomy. 45 (11): 1493–1496. doi:10.1007/s00276-023-03240-6. ISSN 1279-8517. PMC 10587252. PMID 37733018.

[1] Pękala, Przemysław A.; Henry, Brandon M.; Pękala, Jakub R.; Hsieh, Wan Chin; Vikse, Jens; Sanna, Beatrice; Walocha, Jerzy A.; Tubbs, R. Shane; Tomaszewski, Krzysztof A. (2017). "Prevalence of foramen arcuale and its clinical significance: a meta-analysis of 55,985 subjects". Journal of Neurosurgery Spine. 27 (3): 276–290. doi:10.3171/2017.1.SPINE161092. ISSN 1547-5646. PMID 28621616.

[2] Tangrodchanapong, Taweesak; Yurasakpong, Laphatrada; Suwannakhan, Athikhun; Chaiyamoon, Arada; Iwanaga, Joe; Tubbs, R. Shane (2023). "Basilar tubercles and eminences of the clivus: Novel anatomical entities". Annals of Anatomy = Anatomischer Anzeiger: Official Organ of the Anatomische Gesellschaft. 250 152133. doi:10.1016/j.aanat.2023.152133. ISSN 1618-0402. PMID 37460045.

[3] Klepinowski, Tomasz; Osiowski, Aleksander; Grzyb, Weronika; Esposito, Giuseppe; Osiowski, Maksymilian; Klepinowska, Marta; Taterra, Dominik; Sagan, Leszek (2026-01-08). "Prevalence of os odontoideum: a systematic review, meta-analysis and meta-regression with implications for vertebral artery and osseous anomalies". Neurosurgical Review. 49 (1): 112. doi:10.1007/s10143-025-04042-7. ISSN 1437-2320. PMC 12783242. PMID 41504791.

[4] Chaweeborisuit, Phanthip; Yurasakpong, Laphatrada; Kruepunga, Nutmethee; Tubbs, R. Shane; Chaiyamoon, Arada; Suwannakhan, Athikhun (2023). "The prevalence of Stafne bone cavity: A meta-analysis of 355,890 individuals". Journal of Dental Sciences. 18 (2): 594–603. doi:10.1016/j.jds.2022.08.022. ISSN 2213-8862. PMC 10068378. PMID 37021232.

[5] Srichaphan, Narathip; Yurasakpong, Laphatrada; Taradolpisut, Napawan; Senarai, Thanyaporn; Kruepunga, Nutmethee; Suwannakhan, Athikhun (2024). "The thyroid foramen: a systematic review and meta-analysis". Surgical and Radiologic Anatomy. 46 (10): 1673–1681. doi:10.1007/s00276-024-03470-2. ISSN 1279-8517. PMID 39191992.

[6] Lee, Rebecca; Pang, Stephen C.; Borman, William H.; Herrin, Sean O.; Bale, Logan S. W. (2022-10-01). "A prevalence study of the atlantomastoid muscle". Surgical and Radiologic Anatomy. 44 (10): 1349–1353. doi:10.1007/s00276-022-03022-6. ISSN 1279-8517. PMID 36155834.

[7] Yurasakpong, Laphatrada; Nantasenamat, Chanin; Janta, Sirorat; Eiamratchanee, Pinthusorn; Coey, James; Chaiyamoon, Arada; Kruepunga, Nutmethee; Senarai, Thanyaporn; Langer, Martin Franz; Meemon, Krai; Suwannakhan, Athikhun (2022). "The decreasing prevalence of the thyroid ima artery: A systematic review and machine learning assisted meta-analysis". Annals of Anatomy. 239 151803. doi:10.1016/j.aanat.2021.151803. ISSN 1618-0402. PMID 34265384.

[8] Bruna-Mejias, Alejandro; Salazar-Ferrari, Martina; Silva-Garay, Antonia; Chacon Valdebenito, Ignacia Belen; Ortiz -Ahumada, Cynthia; Trujillo-Riveros, Martin; Loaiza-Giraldo, Jessica Paola; Nova- Baeza, Pablo; Orellana- Donoso, Mathias; Santana- Machuca, Andres; Cifuentes-Suazo, Gloria; Oyanedel-Amaro, Gustavo; Paton, Glen; Nalla, Shahed; Valenzuela-Fuenzalida, Juan José (2026-06-01). "Occipitalization of the atlas: prevalence, functional and anatomical considerations. A systematic review and meta-analysis". Translational Research in Anatomy. 43 100465. doi:10.1016/j.tria.2026.100465. hdl:10550/122403. ISSN 2214-854X.

[9] Zielinska, Nicol; Karauda, Piotr; Węgiel, Andrzej; Szewczyk, Bartłomiej; Olewnik, Łukasz (2023-11-01). "A very rare case of a thoracobrachialis muscle". Surgical and Radiologic Anatomy. 45 (11): 1493–1496. doi:10.1007/s00276-023-03240-6. ISSN 1279-8517. PMC 10587252. PMID 37733018.

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