CASE REPORT
Bilateral Internal Carotid Artery Hypoplasia with Craniofacial Anomalies: A Case of Suspected Treacher Collins Syndrome
2023 Volume 10 Pages 55-60
Details
2023 Volume 10 Pages 55-60
Internal carotid artery aplasia or hypoplasia above the cervical bifurcation is rare, occurring in less than 0.01% of the general population. Unilateral neurocristopathy complicated by unilateral internal carotid artery agenesis or hypogenesis has been reported, but bilateral internal carotid artery hypoplasia is rare and scarcely reported. Herein, we report a novel case of Treacher Collins syndrome complicated by bilateral internal carotid artery hypoplasia. A 94-year-old woman presented with complaints of headache and vomiting. Computed tomography revealed a subarachnoid hemorrhage and dysplasia of the bilateral zygoma, mandible, and external auditory meatus. The patient had severe hearing loss and visual impairment. Computed tomography angiography revealed bilateral internal carotid artery hypoplasia and multiple aneurysmal changes in the intracranial arteries. We diagnosed the patient with a ruptured anterior inferior cerebellar artery aneurysm and performed coil embolization. The patient's unique facial features were consistent with neurocristopathy, especially Treacher Collins syndrome. Developmental anomalies of neural crest cells can present as vascular abnormalities and craniofacial malformations. Special care is required for endovascular treatment and airway management in cases of neurocristopathy because of the specific craniofacial anomalies.
Congenital aplasia or hypoplasia of the internal carotid artery (ICA) is rare, occurring in less than 0.01% of the general population.1) Unilateral ICA aplasia or hypoplasia is more common than bilateral ICA aplasia or hypoplasia. Because collateral cerebral blood flow can compensate for the ICA territory, not all cases of ICA aplasia or hypoplasia are associated with ischemic stroke. However, in patients with ICA aplasia or hypoplasia, the incidence of intracranial aneurysms, which may cause subarachnoid hemorrhage (SAH), is 27.8% and is significantly higher than that (2%-4%) in the general population.2) Therefore, it is important to screen for intracranial aneurysms in patients with ICA aplasia or hypoplasia.3,4)
Some abnormalities of the craniocervical arteries are associated with neurocristopathy, a developmental abnormality of neural crest cells that can present with vascular abnormalities and craniofacial malformations.5,6) The Goldenhar syndrome (GS), caused by abnormalities in the first and second branchial arches, is a type of neurocristopathy. Several studies have reported unilateral facial anomalies due to GS complicated with unilateral ICA aplasia or hypoplasia.7-9)
Treacher Collins syndrome (TCS) is another neurocristopathy that occurs because of the developmental inhibition of the first branchial arch and causes downward-sloping palpebral fissures; hypoplasia of the zygomatic bone, mandible, and cleft palate; and lower eyelid coloboma. Abnormalities in the middle ear ossicles could result in conductive hearing loss.10) To the best of our knowledge, only a few reports focused on TCS complicated by bilateral ICA hypoplasia exist. Herein, we report a rare case of bilateral ICA hypoplasia with craniofacial abnormalities suggestive of TCS. The procedures followed in experiments on human subjects were conducted in accordance with the "Ethical Guidelines for Medical and Health Research Involving Human Subjects (Provisional Translation as of March 2015) " and its later amendments. Ethical approval was provided by our Institutional Ethics Committee, and written informed consent was obtained from the patient's family.
A 94-year-old woman with congenital craniofacial dysplasia presented to our hospital with complaints of headache and vomiting for a day. She had no family history of hereditary or vascular disorders. The patient had severe hearing loss and visual impairment, which made communication difficult. In addition, the patient had spontaneous eye opening but was unable to follow instructions, making detailed evaluation of neurological findings difficult. Head computed tomography (CT) revealed SAH, particularly in the right prepontine cistern, and aneurysm-like structures in the interpeduncular cistern (Fig. 1a, b). The diameters of the hypoplastic ICAs were 2.9 mm (right) and 3.4 mm (left) (Fig. 1c). The right external auditory meatus and nasal cavity were obstructed (Fig. 1d). Bone CT showed bilateral zygomatic bone and mandible hypoplasia (Fig. 1e, f). CT angiography (CTA) revealed bilateral ICA hypoplasia (Fig. 2a, b). Aneurysmal changes in the basilar artery tip, right ICA terminal segment, and right anterior inferior cerebellar artery (AICA) origin were also detected on CTA (Fig. 2c). A thick hematoma was identified in the right prepontine cistern, and a bleb was located only on the AICA aneurysm. We did not find any obvious pearl and string signs in the basilar artery or AICA. In addition, there was no false lumen on angiography images. Therefore, the AICA aneurysm was judged to be a saccular aneurysm rather than a dissecting aneurysm. We made a diagnosis of SAH due to a ruptured AICA aneurysm, and the patient underwent coil embolization (Fisher grade 3). Because of the hypoplasia of the mandible, airway management under local anesthesia and sedation was considered difficult. Therefore, surgery was performed under general anesthesia. A 4-Fr guiding sheath was placed in the right brachial artery, and a guiding catheter was inserted. A Tactics (Technocrat Corporation, Aichi, Japan) /Excelsior SL-10 Microcatheter (Stryker Neurovascular, Fremont, USA) /0.014 Transend EX SOFT TIP guidewire (Endeavor; Boston Scientific/Target, Fremont, CA) was coaxially guided into the aneurysm, and eight coils were used for embolization. The surgery was completed once we confirmed the absence of blood flow through the aneurysm and an intact AICA (Fig. 3a-d).
Computed tomography images.
Head computed tomography (CT) revealing subarachnoid hemorrhage, primarily in the right prepontine cistern, and aneurysm-like structures in the interpeduncular cistern (a, b). The bilateral carotid canals are hypoplastic (right, 2.9 mm; left, 3.4 mm) (c), and the right nasal cavity is obstructed (d, white arrow). Bone CT revealing hypoplasia of the bilateral zygomatic bone and mandible (e, f).
Computed tomography angiography images.
Computed tomography angiography (CTA) revealing bilateral internal carotid artery (ICA) hypoplasia above the cervical bifurcation (a, b). Aneurysmal changes at the basilar artery tip (black arrowhead), right ICA terminal segment (white arrowhead), and right anterior inferior cerebellar artery (AICA) origin (white arrow) can be seen on the CTA image (c).
ECA, external carotid artery
Vertebral angiograms.
Right vertebral angiograms revealing aneurysmal changes at the basilar artery tip (black arrowhead) and right anterior inferior cerebellar artery (AICA) origin (white arrow) (a, b).
Eight coils were used to embolize the right AICA aneurysm (c: preoperative; d: postoperative).
The patient had preoperative aspiration pneumonia and was extubated after respiratory management was performed until the sixth postoperative day. The initial damage caused by SAH and pneumonia did not improve the patient's consciousness state, and her respiratory condition worsened because of airway obstruction due to mandibular and nasal cavity dysplasia. The patient's family did not wish for invasive resuscitation. The patient died on postoperative day 14.
Herein, we presented a case of bilateral ICA hypoplasia with craniofacial abnormalities, manifesting as SAH due to a ruptured AICA aneurysm. This case had several unique features. First, the patient had craniofacial abnormalities, clinically diagnosed as TCS. Second, abnormalities of the craniocervical arteries and posterior circulation and bilateral ICA hypoplasia were also found. To our knowledge, this is the first reported case of bilateral ICA hypoplasia with craniofacial abnormalities suggestive of TCS.
ICA aplasia or hypoplasia is a rare congenital anomaly. ICA hypoplasia is more common on the left than on the right side, whereas bilateral hypoplasia is very rare. Although the exact etiology of ICA aplasia or hypoplasia remains unclear, studies have demonstrated that the complex embryologic process governing ICA formation might be associated with ICA malformations.11) Lie described a classification of intracranial ICA aplasia and hypoplasia.12) The carotid canal is absent in cases of aplasia and is small or poorly developed in cases of hypoplasia.13) Cadaver dissection showed that the vertical carotid artery diameter was 4.0-7.5 (mean, 5.7) mm and the horizontal carotid artery diameter was 4.5-7.0 (mean, 5.6) mm.14) The bilateral carotid canals in the present patient were both less than 5 mm in each, the remnant ICA end was observed bilaterally, and a steep transition from the posterior communicating artery to the middle cerebral artery suggested hypoplasia of the ICA. On the basis of the angiographical data, this case was classified as type E.12)
Some craniocervical artery abnormalities are associated with neurocristopathy, a developmental abnormality of neural crest cells. The neural crest, called the fourth germ layer, is divided into the cranial, vagal, trunk, and sacral layers. Cranial neural crest cells migrate to the first and second pharyngeal arches. The first pharyngeal arch divides into maxillary and mandibular prominences, giving rise to the masticatory muscles, zygoma, mandible, malleus, and incus, and is innervated by the trigeminal nerve. The second pharyngeal arch gives rise to the facial muscles, stapes, and facial nerve. Cranial neurocristopathy is associated with facial abnormalities. Endothelial cells comprising the inner layer of all blood vessels are derived from mesodermal precursors, whereas the outer layer cells are derived from the mesoderm in the body or the neural crest cells in parts of the head.15) Therefore, developmental abnormalities of neural crest cells can present with craniofacial malformations and vascular abnormalities.
The craniofacial anomalies of the present patient suggested neurocristopathy. The clinical characteristics of TCS, including a peculiar facial appearance due to the dysplasia of the bilateral zygomatic bones and mandibles, accompanied by visual, and hearing impairment, were present in this case. As the patient had natural severe hearing loss and the right external auditory foramen was obstructed, we concluded that the hearing loss was congenital and not age-related. Although there are cases of decreased quality of life due to hearing and vision loss, the development of the central nervous system is not directly affected in some patients, and they can live a normal life without intellectual disability. Organs derived from the neural crest are potentially affected in neurocristopathy. In TCS, complications such as atrial, and ventricular septal defects, patent ductus arteriosus, aortic coarctation, and Valsalva sinus aneurysm have been reported. There are no apparent differences between patients with TCS and controls in terms of body size or blood diagnostic values. TCS is caused by mutations of the TCOF1 gene (5q32), which encodes the treacle protein, a nucleolar phosphoprotein, or the POLR1C (6p21.1) or POLR1D (13q12.2) genes that encode subunits of the RNA polymerases I and III. The diagnosis of TCS is based on physical examination and molecular genetic testing. In the present case, although a definitive diagnosis using genetic tests could not be made, the clinical characteristics were strongly suggestive of TCS.
A literature search revealed five reported cases of ICA aplasia or hypoplasia with craniofacial anomalies (Table 1). Including our case, the patients' ages ranged from 7 months to 94 years, with facial abnormalities, and ICA aplasia or hypoplasia diagnosed early in life in four of the patients. The associated diseases were considered neurocristopathies. Various methods were used for vascular evaluation, including angiography, and magnetic resonance angiography. The absence of the carotid canal on CT images indicated ICA agenesis. Interestingly, the laterality of the facial abnormalities did not always correspond to that of the vascular abnormalities.
| Author (year) | Age (y or mo)/sex | Facial anomaly (laterality) | Backgrounds that led to craniocervical vascular evaluation | ICA anomaly | Carotid canal | Laterality of facial and vascular abnormalities |
|---|---|---|---|---|---|---|
| F, female; GS, Goldenhar syndrome; HFM, hemifacial microsomia; ICA, internal carotid artery; M, male; MRI, magnetic resonance imaging; OAVS, oculo-auricular-vertebral spectrum; TCS, Treacher Collins syndrome | ||||||
| Robinson (1987)18) | 2 y/M | HFM (Left) | Postmortem angiography at the age of 4 y | Left ICA hypoplasia | Unknown | Ipsilateral |
| Legius (1993)19) | 50 y/M | OAVS (Right) | Examination of hemifacial microsomia and vertebral defects | Left ICA aplasia | Absent | Contralateral |
| Ottaviano et al. (2007)7) | 6 y/F | GS (Right) | Examination of facial anomaly and hypertonus of the lower limbs with reduced motor ability at birth | Right ICA agenesis | Unknown | Ipsilateral |
| Ventura et al. (2014)8) | 7 y/F | GS (Left) | Preoperative MRI for severe left mandibular condyle hypoplasia | Right ICA agenesis | Absent | Contralateral |
| Modica et al. (2015)9) | 7 mo/M | GS (Left) | Evaluation of hemifacial microsomia and anotia | Left ICA agenesis | Absent | Ipsilateral |
| Present case | 94 y/F | Suspected TCS (Bilateral) | Subarachnoid hemorrhage | Bilateral ICA hypoplasia | Hypoplasia | Ipsilateral |
In the present case, the patient died of pneumonia and airway compromise. Neurocristopathy with mandibular hypoplasia, including TCS, is associated with a high risk of airway symptoms, such as those associated with obstructive sleep apnea syndrome, that can occasionally be life-threatening.16,17) Tracheotomy should be considered if extubation is considered difficult, although it was not performed in this case. With proper treatment, the lifelong prognosis of TCS is generally good, with some patients exhibiting no intellectual developmental abnormalities. The present patient was very old and had complex problems, including mandibular hypoplasia, and right nasal cavity obstruction. The patient required perioperative nasogastric intubation through the left nasal cavity. Therefore, her breathing was dependent on the oral airway. However, her respiration apparently deteriorated because of glossoptosis caused by mandibular hypoplasia. Routine cerebrovascular evaluations had not been performed when the patient was born. Treating vascular disorders complicated by neurocristopathy requires complex considerations for airway management and in-depth knowledge of the vascular anatomy.
In conclusion, we have reported a rare case of bilateral ICA hypoplasia with specific facial abnormalities, clinically diagnosed as TCS. The management of suspected neurocristopathy should include careful consideration of the craniocervical vascular anomalies and airway complications.
We would like to thank Editage for the editorial assistance.
•AICA: anterior inferior cerebellar artery
•CT: computed tomography
•CTA: CT angiography
•GS: Goldenhar syndrome
•ICA: internal carotid artery
•SAH: subarachnoid hemorrhage
•TCS: Treacher Collins syndrome
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