Segmental Agenesis Research Articles

Bilateral Internal Carotid Artery Segmental Agenesis Associated with Persistent Trigeminal Artery, Vascular Ectasia, Abnormal Configuration of Brain Stem and Cerebellum

Bilateral segmental agenesis of the internal carotid artery is a rare developmental anomaly. We report a case of congenital bilateral internal carotid arteries segmental agenesis associated with persistent trigeminal artery, vascular ectasia and abnormal configuration brain stem and cerebellum. We postulate that these findings could result from interference in development during the early stages.

A report of two cases with dolichosegmental intracranial arteries as a new feature of PHACES syndrome

We describe two previously unreported cases with complete or incomplete expression of PHACES syndrome, a rare congenital syndromal pediatric disorder, which is characterized by posterior cranial fossa malformations, large facial hemangiomas, arterial anomalies, coarctation of the aorta and cardiac defects, abnormalities of the eye, sternal and supraabdominal raphe defects. These two children exhibited a feature not reviewed extensively in the literature, namely, segmental elongation and dilatation of intracranial arteries associated with intracranial occlusive arterial disease, predominantly on the anterior division of the internal carotid artery (ICA) and on the P2 segment of the posterior cerebral artery. This dolichoectasia was found at the distal cervical internal carotid artery, the intradural segment of the ICA before the division, the trigeminal artery, and the posterior division of the ICA. We presume that the different forms of arterial involvement in PHACES syndrome (arterial stenoses, segmental agenesis of vessels, and the dolichoectasia described in this study) constitute a spectrum of angiogenetic dysfunctions related to an embryonic event involving several cephalic neural crest segments of the dorsal aorta.

Spinal dysraphism: MR imaging rationale

Spinal cord development occurs through the three consecutive periods of gastrulation (weeks 2-3), primary neurulation (weeks 3-4), and secondary neurulation (weeks 5-6). Spinal cord malformations derive from defects in these early embryonic stages, and are collectively called spinal dysraphisms. Spinal dysraphisms may be categorized clinically into open and closed, based on whether the abnormal nervous tissue is exposed to the environment or covered by skin. Open spinal dysraphisms include myelomeningocele and other rare abnormalities such as myelocele, hemimyelomeningocele, and hemimyelocele, and are always associated with a Chiari II malformation. Closed spinal dysraphisms are further divided into two subsets based on whether a subcutaneous mass is present in the low back. Closed spinal dysraphisms with mass comprise lipomyelocele, lipomyelomeningocele, meningocele, and myelocystocele. Closed spinal dysraphisms without mass comprise simple dysraphic states (tight filum terminale, filar and intradural lipomas, persistent terminal ventricle, and dermal sinuses) and complex dysraphic states. The latter category involves abnormal notochordal development, either in the form of failed midline integration (ranging from complete dorsal enteric fistula to neurenteric cysts and diastematomyelia) or of segmental agenesis (caudal agenesis and spinal segmental dysgenesis). Magnetic resonance imaging is the imaging modality of choice for evaluation of this complex group of disorders.

Segmental Spinal Dysgenesis: A Report of Three Cases

Segmental spinal dysgenesis is an uncommon congenital spinal defect characterized by localized segmental agenesis of the upper lumbar or thoracolumbar spine. Bony defects include significant focal canal stenosis, hypoplastic or absent vertebrae, subluxation of the spinal column, and instability. The distal bony architecture is usually normal but may be bifid. There is significant narrowing of the thecal sac and absence of adjacent nerve roots at the level of the lesion. Distal neurologic deficits are variable in severity, the prevalence of neurogenic bladder is high, and associated anomalies are common. Progressive kyphosis is inevitable. The cause is unknown, but an association with maternal diabetes and with various medications and toxins has been noted. Other authors suggested a relation to an aberrant segmental vascular supply. Treatment should be directed at the establishment and maintenance of spinal stability and arrest of the progressive kyphosis. It should consist of early anterior and posterior arthrodesis, with or without anterior decompression of the cord. Accurate visualization of this unusual deformity is difficult with conventional radiographic techniques. Three-dimensional computerized tomographic reconstruction can therefore be invaluable in preoperative planning. We report three cases of segmental spinal dysgenesis, all of which have been uniquely detailed by striking three-dimensional imaging studies.

Radiologic anatomy of segmental agenesis of the internal carotid artery

Radiologic anatomy of segmental agenesis of the internal carotid artery

Radiologic anatomy of segmental agenesis of the internal carotid artery.

We report six cases of segmental agenesis of the internal carotid a. discovered in adult patients: one case of cervical segmental agenesis (no. 1), one case of cervical and petrosal segmental agenesis (no. 2), two cases of vertical cavernous segmental agenesis (nos. 3 and 4) and two cases of distal segmental agenesis, one unilateral (no. 5) and the other bilateral (no. 6). The collateral pathways observed were: the ascending pharyngeal a. which constitutes an "intratympanic course" of the internal carotid a. (no. 1), an intercarotid anastomosis (no. 2), an arterial network at the base of the skull, the so-called "rete mirabile" (nos. 3 and 4) and the posterior communicating a. (nos. 5 and 6). Recognition of these rare dysgenesis relies upon the following radio-anatomic characteristics: reduced caliber of the a., inconsistent sparing of the carotid body, reduced diameter or even absence of the carotid canal and above all, the presence of collateral pathways. The collateral pathways allow an understanding of the segmental nature of carotid a. development and a distinction between congenital and acquired stenoses.

Multiple segmental agenesis of the cerebral arteries: case report

Multiple segmental agenesis of the cerebral arteries: case report

Agenesis of the cervical internal carotid artery

Total or segmental agenesis of the internal carotid artery is a rare anomaly. Cervical portion of the internal carotid artery was abscent in the right side of the patient who underwent radical surgery due to recurrent oropharyngeal cancer. Postoperative venous digital subtraction angiography revealed that the remaining intracranial portion of the internal carotid artery was normally patent and supplied blood flow via ipsilateral external carotid artery. Head and neck surgeon should be aware of such a vasucular anomaly to avoid a disastrous result caused by ligation of the extrenal carotid artery.

Poland's anomaly. Natural history and long-term results of chest wall reconstruction in 33 patients.

Poland's anomaly is an uncommon congenital aberration of the chest wall characterized by absence of the pectoralis major muscle and other nearby musculoskeletal components. In this series, a wide spectrum of thoracic deformities was associated with the Poland anomaly, ranging from segmental agenesis of the ribs, sternum, and nearby muscles, to simple aplasia of the pectoralis major muscle. Although little disability was associated with the syndrome, the patients primarily sought operative correction due to the asymmetry and their perception of adverse cosmesis. Over a 10-year period, 53 operations were performed on 27 individuals with the goal of correcting the abnormal contour of the chest wall. The most successful reconstructions involved the use of the latissimus dorsi muscle, which was detached and transferred to the anterior chest wall while preserving the neurovascular pedicle. In women, this was accompanied by insertion of a mammary prosthesis. Reconstruction of the so-called "herniation" of the lung with rib grafts or alloplastic materials was found to be unnecessary, and the use of custom-made chest wall prostheses is not recommended, since four of five of these devices had to be removed due to migration, erosion of local tissues, and adverse cosmesis.

Intracavernous branches of the internal carotid artery (ICA). Comprehensive review of their variations.

Since we started to work in the lateral sellar region (in 1973), a large volume of angiographic material has provided us with exceptional variations that added to the anatomic facts obtained from our dissections. At present, these anatomic facts remain, but the way we look at them and the way we use them for endovascular treatments, has created a need for a different type of approach and understanding. In this report, we present a flexible anatomical view of the intracavernous branches of the internal carotid artery and a scheme to understand and predict the anatomical variations of these collaterals. Four embryonic vessels play an important role in the variations of the arterial supply to the lateral cavernous region: the dorsal ophthalmic artery, the stapedial artery, the trigeminal artery and the primitive maxillary artery. In general each of them partially regresses leaving behind a remnant. However there is a spectrum from their persistence to incomplete regression, resulting in variations of the supply to their distal territories. The term "meningohypophyseal" should be abandoned because it is misleading and improperly used. Complete agenesis is known for a long time; in case of segmental agenesis of the ICA each of the embryonic vessels presented above may represent an alternate route to bypass the agenesis. The ICA is not a direct feeding artery but a succession of independant segments which can be the site of various anomalies. An embryonic transdural circle can be individualized; it is constituted by the trigeminal arteries posteriorly, the ICA siphon anteriorly, the transsellar anastomosis and internal maxillary artery connections. Although regressions usually occur in this embryonic transdural circle, its derivatives congenital and acquired arterial pathologies. It also constitutes the key system in determining the arterial variations of the perisellar region.

Equivocal amniotic fluid levels of alpha fetoprotein in prenatal diagnosis of neural tube defects

The following case is reported as an example of problems of interpreting alpha fetoprotein (AFP) results of amniocentesis. A 26-year-old underwent amniocentesis at 16 weeks of gestation because a previous infant had been born with myelomeningocele. Sonography revealed the placenta posteriorly implanted and there was no evidence of twin gestation. The fluid was clear and AFP was measured at 2.75 mg% (upper limit of normal 2.3 mg%). The results were called borderline abnormal and amniography was suggested to the patient to attain a diagnosis but the patient decided on termination without supporting tests. The fetus was found to have a lumbar spina bifida with myeloschisis and segmental agenesis of the lumbar spinal cord. A borderline measurement (greater than 2 standard deviations above normal) requires further testing before diagnosis can be made.

Segmental Agenesis of Inferior Vena Cava with Azygos Substitution: Angiographic Findings

Segmental Agenesis of Inferior Vena Cava with Azygos Substitution: Angiographic Findings

SYMPODIA IN INDENTICAL TWINS. REPORT OF A CASE.

OCCASIONALLY, reports of a rare malformation termed sympodia appear in the literature. The typical case report includes a description, usually fairly standard, of a macerated, stillborn, male fetus, immediately recognizable by fusion of the body from the waist down. It is this deformity which gave the condition the descriptive title of siren or sirenomelus which refers to the mythical mermaids of classical literature. Complete fusion, without vestiges of limbs is more specifically termed sympus apus.1 The internal anatomy also usually shows the characteristic varying degrees of agenesis of the renal and genitourinary tracts, accompanied by malformations and segmental agenesis of the gastrointestinal tract. Malformations superior to the diaphragm2,3are unusual. The present case is noteworthy for several reasons: (1) It occurred in identical twins. A search of the literature failed to disclose any previous reports of this malformation in identical twins. (2) Both infants were viable and in