Answer for BIR CoW 23 Aug 2020
BILATERAL ICA HYPOPLASIA
IMAGING FINDINGS
Plain CT Brain Hemorrhage in the bilateral lateral ventricles & third ventricle with extension into the right peritrigonal region.
MRI Brain - Subarachnoid haemorrhage along the bilateral parietal and occipital regions. There is subacute bleed within the bilateral lateral ventricles, 3rd and 4th ventricles.
Non contrast MR angiogram revealed diffusely thin calibre of bilateral internal carotid arteries with ectasia of the vertebrobasilar system with flow related aneurysms in basilar artery and left PCOM. CT Cerebral Angiogram - Diffuse hypoplasia of the bilateral cervical and intracranial internal carotid arteries. Enlarged and ectatic bilateral vertebral arteries and left PCOM with multiple saccular and fusiform aneurysms in the basilar and left PCOM - likely flow related aneurysms due to compensatory flow.
DISCUSSION
Hypoplasia of the internal carotid artery is a rare congenital anomaly with only few cases described in the literature. Mostly of them are usually unilateral and and accounting for < 0.01 % of the population. Some of the cases are bilateral and remain asymptomatic due to rich collateral supply.Due to the presence of rich collateral supply, increased blood flow and velocity with haemodynamic alternation, these patients are more prone to develop intracranial aneurysms as compared with the general population. Lie et al described six compensatory collateral circulations in congenital anamolies of ICA which include: Type A, Unilateral ICA agenesis: The anterior communicating artery compensates to the ipsilateral anterior cerebral artery and the enlarged posterior communicating artery to the ipsilateral middle cerebral artery. Type B: Ipsilateral anterior cerebral artery and middle cerebral artery are supplied by the anterior communicating artery. Type C: Bilateral hypoplasia of ICA. The anterior circulation of ICA blood supply is compensated by the carotid-vertebrobasilar artery anastomosis of the basilar artery. Type D: Unilateral hypoplasia of ICA, blood is supplied to the ipsilateral carotid siphon from the cavernous sinus anastomosis. Type E: Bilateral ICA hypoplasia, the small anterior cerebral artery is supplied by bilateral ICA and the middle cerebral artery is supplied by an expanded posterior communicating artery. Type F: Distal collateral circulation through external carotid artery, internal maxillary artery and skull base anastomosis. Symptomatic patients usually present with various symptoms like transient ischemic attacks, infarct, seizures, aneurysmal subarachnoid hemorrhage, or parenchymal bleeds. Imaging Features: Cross sectional imaging modalities like computed tomography, Magnetic resonance imaging can help us suggest the diagnosis. Non contrast MR angiogram reveals the small caliber of the bilateral internal carotid arteries and the presence of aneurysms and the collateral vessels. 3D CT angiogram is a non invasive technique, with the volume rendered and surface shaded images can be used as a pre- operative road map for the management of the aneurysms. Non contrast CT in bone window helps in differentiating absence of internal carotid artery from hypoplasia. In congenital absence of ICA, the osseous carotid canals are usually absent and in hypoplasia the carotid canals are also hypoplastic However Digital subtraction angiography is the gold standard method for the confirmation of diagnosis and for the detection of complications like flow related aneuryms and collaterals.
Management:
There is no protocol for the management of asymptomatic patients with bilateral internal carotid artery and follow up with imaging will suffice to look for aneurysms. However symptomatic patients and those with aneurysms need intervention in order to prevent intracranial bleed.
References:
1. Lie TA. Congenital anomalies of the carotid arteries. Amsterdam: Excerpta Medica Foundation. 1968. pp. 35–51.
2. Given CA, 2nd, Huang-Hellinger F, Baker MD, Chepuri NB, Morris PP. Congenital absence of the internal carotid artery: Case reports and review of the collateral circulation. AJNR Am J Neuroradiol. 2001;22:1953–9
3. Steer AC, Rowe PW. Bilateral agenesis of the internal carotid artery: case report and approach to management. J Paediatr Child Health. 2008;44(9):511-3.
IMAGING FINDINGS
Plain CT Brain Hemorrhage in the bilateral lateral ventricles & third ventricle with extension into the right peritrigonal region.
MRI Brain - Subarachnoid haemorrhage along the bilateral parietal and occipital regions. There is subacute bleed within the bilateral lateral ventricles, 3rd and 4th ventricles.
Non contrast MR angiogram revealed diffusely thin calibre of bilateral internal carotid arteries with ectasia of the vertebrobasilar system with flow related aneurysms in basilar artery and left PCOM. CT Cerebral Angiogram - Diffuse hypoplasia of the bilateral cervical and intracranial internal carotid arteries. Enlarged and ectatic bilateral vertebral arteries and left PCOM with multiple saccular and fusiform aneurysms in the basilar and left PCOM - likely flow related aneurysms due to compensatory flow.
DISCUSSION
Hypoplasia of the internal carotid artery is a rare congenital anomaly with only few cases described in the literature. Mostly of them are usually unilateral and and accounting for < 0.01 % of the population. Some of the cases are bilateral and remain asymptomatic due to rich collateral supply.Due to the presence of rich collateral supply, increased blood flow and velocity with haemodynamic alternation, these patients are more prone to develop intracranial aneurysms as compared with the general population. Lie et al described six compensatory collateral circulations in congenital anamolies of ICA which include: Type A, Unilateral ICA agenesis: The anterior communicating artery compensates to the ipsilateral anterior cerebral artery and the enlarged posterior communicating artery to the ipsilateral middle cerebral artery. Type B: Ipsilateral anterior cerebral artery and middle cerebral artery are supplied by the anterior communicating artery. Type C: Bilateral hypoplasia of ICA. The anterior circulation of ICA blood supply is compensated by the carotid-vertebrobasilar artery anastomosis of the basilar artery. Type D: Unilateral hypoplasia of ICA, blood is supplied to the ipsilateral carotid siphon from the cavernous sinus anastomosis. Type E: Bilateral ICA hypoplasia, the small anterior cerebral artery is supplied by bilateral ICA and the middle cerebral artery is supplied by an expanded posterior communicating artery. Type F: Distal collateral circulation through external carotid artery, internal maxillary artery and skull base anastomosis. Symptomatic patients usually present with various symptoms like transient ischemic attacks, infarct, seizures, aneurysmal subarachnoid hemorrhage, or parenchymal bleeds. Imaging Features: Cross sectional imaging modalities like computed tomography, Magnetic resonance imaging can help us suggest the diagnosis. Non contrast MR angiogram reveals the small caliber of the bilateral internal carotid arteries and the presence of aneurysms and the collateral vessels. 3D CT angiogram is a non invasive technique, with the volume rendered and surface shaded images can be used as a pre- operative road map for the management of the aneurysms. Non contrast CT in bone window helps in differentiating absence of internal carotid artery from hypoplasia. In congenital absence of ICA, the osseous carotid canals are usually absent and in hypoplasia the carotid canals are also hypoplastic However Digital subtraction angiography is the gold standard method for the confirmation of diagnosis and for the detection of complications like flow related aneuryms and collaterals.
Management:
There is no protocol for the management of asymptomatic patients with bilateral internal carotid artery and follow up with imaging will suffice to look for aneurysms. However symptomatic patients and those with aneurysms need intervention in order to prevent intracranial bleed.
References:
1. Lie TA. Congenital anomalies of the carotid arteries. Amsterdam: Excerpta Medica Foundation. 1968. pp. 35–51.
2. Given CA, 2nd, Huang-Hellinger F, Baker MD, Chepuri NB, Morris PP. Congenital absence of the internal carotid artery: Case reports and review of the collateral circulation. AJNR Am J Neuroradiol. 2001;22:1953–9
3. Steer AC, Rowe PW. Bilateral agenesis of the internal carotid artery: case report and approach to management. J Paediatr Child Health. 2008;44(9):511-3.
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!