History : 53 year male came with history of headache

Fig 1: Enlarged, tortous, high riding basilar artery

Fig 2 : High bifurcation of basilar artery

Fig 3 :Basilar artery aneurysm

Fig 4 : Right sided arch with separate origin of major arteries.

Fig 5 : Right sided aortic arch

Fig 6 : Aberrant left subclavian artery with separate origins of both subclavian and both comman carotid arteries

FINAL DIAGNOSIS :
Right sided aortic arch with aberrant left subclavian artery with vertebrobasilar dolichoectasia with fusiform aneurysm of basilar artery.

DISCUSSION

Right sided aortic arch :
Several types of vascular rings have aortic arches that are right sided. Although the specific anatomic details of the various forms differ, they share the defining feature of all vascular rings, namely, encirclement of the trachea and esophagus by connected segments of the aortic arch and its branches. A right aortic arch may occur without forming a vascular ring.

Embryology
Early in the course of embryonic morphogenesis, 6 pairs of pharyngeal arch arteries develop in conjunction with the branchial pouches. The segments of the bilateral aortic arch system that normally regress include the distal portion of the sixth arch and the right-sided dorsal aorta. Normally, the left fourth arch becomes the aortic arch, the right fourth arch contributes to the innominate artery, the distal left sixth arch becomes the ductus arteriosus, the proximal sixth arches bilaterally contribute to the proximal branch pulmonary arteries, the left dorsal aorta becomes the descending thoracic aorta, and the dorsal intersegmental arteries bilaterally become the subclavian arteries.

A right aortic arch is formed when the right dorsal aorta remains patent and either the left fourth arch or the left dorsal aorta regress abnormally.

Anatomy
Vascular ring with a right aortic arch has 2 primary forms and 2 other forms that are much less common. In the most frequent form of vascular ring with a right aortic arch, an aberrant origin of the left subclavian artery from a retroesophageal diverticulum (diverticulum of Kommerell) is present, which originates as the last branch of the aortic arch (distal to the right subclavian artery). The ring is completed by a left-sided ductus arteriosus (or its remnant ligamentum arteriosum) passing from the aberrant left subclavian artery to the proximal left pulmonary artery. The retroesophageal diverticulum is distinguished from the aberrant left subclavian artery by its larger caliber.

In the second major type of vascular ring with a right aortic arch, the brachiocephalic vessels originate from the arch in mirror-image fashion with the left innominate artery the first branch followed by the right common carotid and subclavian arteries. A left-sided ductus arteriosus or ligamentum arteriosum passes between the descending aorta and the proximal left pulmonary artery. In contrast to right aortic arch with aberrant left subclavian artery from a retroesophageal diverticulum, the descending aorta usually crosses to the left side of midline proximally in its course, although in rare cases, it remains to the right of midline until reaching the lower portion of the thorax.

A rare form of vascular ring with a right aortic arch is a right arch with an aberrant retroesophageal innominate artery arising as the last branch of the arch and then giving off a ductus/ligamentum to the proximal left pulmonary artery.

An uncommon form of right aortic arch that technically is not a vascular ring but may cause symptoms similar to a ring is a right arch with an aberrant left subclavian artery arising as the last branch of the arch and a left-sided descending aorta. The ductus arteriosus is right sided; thus, a ring is not actually formed, but the retroesophageal descending aorta may rarely cause symptomatic airway symptoms, esophageal symptoms, or both.

Associated cardiovascular anomalies
Ventricular septal defect is the most common associated anomaly.

Associated syndromes and noncardiac conditions

1. Band 22q11 deletion is responsible for DiGeorge, velocardiofacial, and conotruncal anomaly face syndromes, which are often referred to by the unified terms CATCH-22 syndrome or chromosome 22q11 deletion syndrome.
2. Occasionally, patients with right aortic arch may have anomalies consistent with either vertebral, anal, cardiac, tracheal, esophageal, renal, and limb (VACTERL) associations or posterior coloboma, heart defect, choanal atresia, retardation, genital, and ear (CHARGE) associations.
3. Congenital laryngeal web is another noncardiac anomaly that may be associated with vascular rings and may present with the same symptoms and signs as a vascular ring.

CLINICAL History
The history of patients with right aortic arch and vascular ring depends on several factors, including the severity of tracheal compression, esophageal compression, or both and whether associated anomalies are present.

DIFFERENTIALS
Asthma,Bronchiolitis,Congenital Stridor,Croup,Laryngomalacia,Pulmonary Artery Sling,Stridor,Tracheomalacia,Vascular Ring, Double Aortic Arch,Laryngeal stenosis
Laryngeal web

Imaging Studies

Chest radiography:
In the anteroposterior projection, the presence of a right aortic arch may be revealed by the location of the aortic knob and the slight leftward deviation of the lower trachea. On the lateral chest radiograph, posterior indentation of the trachea may be revealed.

Echocardiography

MRI and CT scanning: MRI and CT scanning are the best single imaging studies for the diagnosis and characterization of vascular rings.

Angiography: Although angiography was once the criterion standard for the diagnosis of rings, MRI is both less invasive and diagnostically superior.

Barium esophagography: In patients with a right aortic arch, a
right-sided indentation of the esophagus may be observed on the anteroposterior view, depending on the tightness of the ring. Posterior indentation of the esophagus is nearly always present on the lateral view.

TREATMENT :

Medical Care
Medical care before surgical repair depends on the clinical presentation. In most cases, only supportive management is required. Catheter interventions are not used in the management of vascular ring formed by a right aortic arch.

Surgical Care

Indications: Surgical division of the vascular ring is indicated in any patient with symptoms of airway or esophageal compression and in patients undergoing surgery for repair of associated cardiovascular or thoracic anomalies.

Consultations
Unless specific associated anomalies or problems are identified, consultations are generally not necessary. As noted above, band 22q11 deletion is present in a substantial proportion of patients with vascular rings. A consultation with a geneticist is indicated in patients with other characteristic features of the band 22q11 deletion syndrome and may be appropriate in young infants, in whom typical features of the syndrome may not yet be evident.
.
VERTEBROBASILAR DOLICHOECTASIA:
The term dolichoectasia means elongation and distention.
In the vertebrobasilar system this term is appropriately used if the basilar artery courses lateral to the clivus or dorsum sellae or if the bifurcation of the basilar artery occurs above the plane of the suprasellar cisterns. Ectasia implies a basilar artery with a diameter greater than 4.5 mm.

Pathogenesis : probably related to marked thinning of the
internal elastic lamina and media, most likely a consequence of prolonged systemic arterial hypertension.

Clinical presentation of vertebrobasilar dolichoectasia (VBD) :
 Related to the severity of the elongation and ectasia.
Symptoms are related to direct cranial nerve compression, ischemic effects on the brain stem and cerebellar hemispheres as well as symptoms related to hydrocephalus. Direct cranial nerve compression can lead to isolated cranial nerve dysfunction, usually associated with a normal-sized basilar artery that is tortuous and elongated. Isolated cranial nerve dysfunction most commonly involves the VII cranial nerve (hemifacial spasm or paresis) and the V cranial nerve (trigeminal neuralgia). Multiple cranial nerve dysfunction is far more likely to occur if there is dilation (ectasia) associated with a tortuous and elongated basilar artery. Cranial nerves affected in descending order of frequency include: VII, V, III, VIII, and VI. Trigeminal neuralgia associated with hemifacial spasm is one commonly encountered combination.

Imaging modalities for Diagnosis :
CT , MR, and angiography

Cerebral aneurysms:

Background
The word "aneurysm" comes from the Greek word aneurysma (ana meaning across, and eurys meaning broad) and denotes an abnormal dilatation of an artery. Anterior circulation aneurysms arise from the internal carotid artery or any of its branches, whereas posterior circulation aneurysms arise from the vertebral artery, basilar artery, or any of their branches.

Classification:
 saccular and nonsaccular types, according to their shape and etiology. Nonsaccular aneurysms include atherosclerotic, fusiform, traumatic, and mycotic types. Saccular, or berry, aneurysms have several anatomic characteristics that distinguish them from other types of intracranial aneurysms.

Pathophysiology
Currently, the most important pathogenetic factor in aneurysmal formation is considered to be an area of mural degeneration in regions of hemodynamic stress.

Aneurysmal multiplicity
The prevalence of aneurysmal multiplicity is generally higher in autopsy series (25-31%) than in large clinical series (15-24%). Female patients account for 60-81% of those with multiple aneurysms.

Clinical Details
In a review of the literature, 89% of saccular intracranial aneurysms were associated with SAH, 7% were associated with a mass effect, and 4% were incidental findings.

Imaging modalities:
A strong clinical suspicion of aneurysm can be validated by using several diagnostic studies, including CT, lumbar puncture, magnetic resonance imaging (MRI), and cerebral angiography. CT is typically the first diagnostic test ordered when the possibility of SAH exists. Findings on a nonenhanced CT scan can confirm subarachnoid blood in more than 90% of patients with acute SAH. Diffuse, severe SAH is seldom helpful in suggesting the specific site of the aneurysm.

Differentials
Brain, Arteriovenous Malformation
Thunderclap headache
Benign orgasmic cephalgia


References:

• McElhinney DB, McDonald-McGinn D, Zackai EH, Goldmuntz E. Cardiovascular anomalies in patients diagnosed with a chromosome 22q11 deletion beyond 6 months of age. Pediatrics. Dec 2001;108(6):E104.
  
  
• Achiron R, Rotstein Z, Heggesh J, et al. Anomalies of the fetal aortic arch: a novel sonographic approach to in-utero diagnosis. Ultrasound Obstet Gynecol. Dec 2002;20(6):553-7
  
• Inci S, Erbengi A, Ozgen T. Aneurysms of the distal anterior cerebral artery: report of 14 cases and a review of the literature. Surg Neurol. Aug 1998;50(2):130-9; discussion 139-40.
  
  

  Case contributed by

  Dr. Bimal Kumar Saha(junior resident). Dr.Bipin Kulkarni(junior resident). Dr.Teenu Singh(junior resident). Dr.Vinay Satkar(junior resident). Dr.Vikram Chavan(junior resident).

  
  

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