Ponticulus posticus

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A Moment in History

Jean George Bachmann
(1877 – 1959)

French physician–physiologist whose experimental work in the early twentieth century provided the first clear functional description of a preferential interatrial conduction pathway. This structure, eponymically named “Bachmann’s bundle”, plays a central role in normal atrial activation and in the pathophysiology of interatrial block and atrial arrhythmias.

As a young man, Bachmann served as a merchant sailor, crossing the Atlantic multiple times. He emigrated to the United States in 1902 and earned his medical degree at the top of his class from Jefferson Medical College in Philadelphia in 1907. He stayed at this Medical College as a demonstrator and physiologist. In 1910, he joined Emory University in Atlanta. Between 1917 -1918 he served as a medical officer in the US Army. He retired from Emory in 1947 and continued his private medical practice until his death in 1959.

On the personal side, Bachmann was a man of many talents: a polyglot, he was fluent in German, French, Spanish and English. He was a chef in his own right and occasionally worked as a chef in international hotels. In fact, he paid his tuition at Jefferson Medical College, working both as a chef and as a language tutor.

The intrinsic cardiac conduction system was a major focus of cardiovascular research in the late nineteenth and early twentieth centuries. The atrioventricular (AV) node was discovered and described by Sunao Tawara and Karl Albert Aschoff in 1906, and the sinoatrial node by Arthur Keith and Martin Flack in 1907.

While the connections that distribute the electrical impulse from the AV node to the ventricles were known through the works of Wilhelm His Jr, in 1893 and Jan Evangelista Purkinje in 1839, the mechanism by which electrical impulses spread between the atria remained uncertain.

In 1916 Bachmann published a paper titled “The Inter-Auricular Time Interval” in the American Journal of Physiology. Bachmann measured activation times between the right and left atria and demonstrated that interruption of a distinct anterior interatrial muscular band resulted in delayed left atrial activation. He concluded that this band constituted the principal route for rapid interatrial conduction.

Subsequent anatomical and electrophysiological studies confirmed the importance of the structure described by Bachmann, which came to bear his name. Bachmann’s bundle is now recognized as a key determinant of atrial activation patterns, and its dysfunction is associated with interatrial block, atrial fibrillation, and abnormal P-wave morphology. His work remains foundational in both basic cardiac anatomy and clinical electrophysiology.

Sources and references
1. Bachmann G. “The inter-auricular time interval”. Am J Physiol. 1916;41:309–320.
2. Hurst JW. “Profiles in Cardiology: Jean George Bachmann (1877–1959)”. Clin Cardiol. 1987;10:185–187.
3. Lemery R, Guiraudon G, Veinot JP. “Anatomic description of Bachmann’s bundle and its relation to the atrial septum”. Am J Cardiol. 2003;91:148–152.
4. "Remembering the canonical discoverers of the core components of the mammalian cardiac conduction system: Keith and Flack, Aschoff and Tawara, His, and Purkinje" Icilio Cavero and Henry Holzgrefe Advances in Physiology Education 2022 46:4, 549-579.
5. Knol WG, de Vos CB, Crijns HJGM, et al. “The Bachmann bundle and interatrial conduction” Heart Rhythm. 2019;16:127–133.
6. “Iatrogenic biatrial flutter. The role of the Bachmann’s bundle” Constán E.; García F., Linde, A.. Complejo Hospitalario de Jaén, Jaén. Spain
7. Keith A, Flack M. The form and nature of the muscular connections between the primary divisions of the vertebrate heart. J Anat Physiol 41: 172–189, 1907.

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Details: Written by: Fernanda Cortes, DDS, MSc; Published: July 12, 2017; Hits: 5721

Figure A: Incomplete PP viewed from the
posterior aspect of the articular fossa
related to the retroglenoid tubercle

The Ponticulus Posticus (PP), also known as the pons arcuatus, foramen arcuale, and arcuate foramen, is a bony bridge that connects the retroglenoid tubercle with the posterior arch of the C1 vertebra, also known as the Atlas.

It substitutes the lateral segment of the posterior atlantooccipital ligament or joint capsule (1) on the area which stabilizes the vertebral artery on its emergency of the transverse foramen of the Atlas (2). This bridge or arch could be thick, thin or even incomplete (2). The importance of this calcification relies on the fact that it has been linked with cervicogenic headache (1,3) chronic tension-type headaches, sensorineural hearing loss (4), shoulder and arm pain, neck pain, and vertigo (1, 5).

The presence of a ponticulus posticus could also impact the planning of high cervical surgeries associated with the Atlas [C1] (6). A recent meta-analysis of the prevalence of this condition worldwide found an overall prevalence of a complete PP of 9.1% versus an incomplete PP, which was 13.6%. In males (10.4%) the complete PP was more common than in females (7.3%), but an incomplete PP was more commonly seen in females (18.5%) than in males (16.7%) (7).

Figure B: Complete PP. It crosses from the
retroglenoid tubercle down to the
posterior arch.

Despite the fact that this calcification has been associated with different painful disorders, some other authors consider it an anatomical condition destined to protect the vertebral artery and not a pathological condition (8). PP is visible on lateral cervical spine and cranial lateral radiographs as thin bony arch on the shape of a ring crossing from the retroglenoid tubercle to the posterior arch of C1, being either partially of fully calcified (Figures C and D).

Note 1: For the etymology of the term glenoid, click here.
Note 2: Figures C and D can be found at the bottom of the article

Sources:
1. Ross JS, Moore KR, editors. Diagnostic Imaging: Spine E-Book. 3rd ed. Philadeplphia: Elsevier; 2015. 31 p.
2. Torres Cueco R. La Columna Cervical: Evaluación Clínica y Aproximaciones Terapéuticas. Principios anatómicos, funcionales, exploración clínica y técnicas de tratamiento. Tomo I. 1° Ed. Madrid: Medica Panamericana; 2008. 124 p.
3. Tambawala SS, Karjodkar FR, Sansare K, Motghare D, Mishra I, Gaikwad S, Dora AC. Prevalence of Ponticulus Posticus on Lateral Cephalometric Radiographs, its Association with Cervicogenic Headache and a Review of Literature. World Neurosurg [Internet]. 2017 Apr 17(cited 02 Jun 2017). pii: S1878-8750(17)30525-9. Available at: doi: 10.1016/j.wneu.2017.04.030. [Epub ahead of print]
4. Koutsouraki E, Avdelidi E, Michmizos D, Kapsali SE, Costa V, Baloyannis S. Kimmerle's anomaly as a possible causative factor of chronic tension-type headaches and neurosensory hearing loss: Case report and literature review. Int J Neurosci. 2010; 120:236-9
5. Cakmak O, Gurdal E, Ekinci G, Yildiz E, Cavdar S. Arcuate foramen and its clinical significance. Saudi Med J. 2005; 26:1409-13.
6. Song MS, Lee HJ, Kim JT, Kim JH, Hong JT. Ponticulus posticus: Morphometric analysis and Its anatomical Implications for occipito-cervical fusion. Clin Neurol Neurosurg [Internet]. 2017 Jun (cited 02 Jun 2017);157:76-81. Available at: doi: 10.1016/j.clineuro.2017.04.001. Epub 2017 Apr 3.
7. Pękala PA, Henry BM, Pękala JR, Hsieh WC, Vikse J, Sanna B, Walocha JA, Tubbs RS, Tomaszewski KA. Prevalence of foramen arcuale and its clinical significance: a meta-analysis of 55,985 subjects. J Neurosurg Spine [Internet]. 2017 Jun (cited 02 Jun 2017); 16:1-15. Available at: doi: 10.3171/2017.1.SPINE161092. [Epub ahead of print]
8. Schilling J, Schilling A, Suazo I. Ponticulus posticus on the Posterior Arch of Atlas, Prevalence Analysis in Asymptomatic PatientsInt. J. Morphol. 2010 Mar; 28(1):317-322.

Acknowledgments: The Atlas [C1] specimens shown on figures A and B belong to the Anatomy department of the Medical College of the Finis Terrae University, Santiago, Chile and are used to show two examples of PP. With permission.
Article written by Prof. M. Fernanda Cortes, DDS, MsC.

Figure C: Complete PP shown on a lateral radiographic view. Figure D: Partial PP shown on a lateral radiographic view.

Ponticulus posticus

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