CASE 12477 Published on 11.02.2015
0

Bilateral medial thalamic infarcts, a typical finding due to occlusion of the artery of Percheron

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Javier Pereda Rodríguez, Cristina Fernández Rey, Claudia Lorena Martínez Higueros

Complejo Asistencial de Segovia.
Sanidad de Castilla y León. SACYL
Carretera de Ávila, s/n. C.P.
40002. Segovia, Castilla y León, Spain
Email:javierpereda2008@gmail.com
Connected authors
Patient

65 years, male

Categories
Area of Interest Neuroradiology brain ; Imaging Technique MR, CT, MR-Diffusion/Perfusion
Download as PDF Print Show related cases Notify admin
Clinical History
A 65-year-old man, with unremarkable previous history, was brought to the hospital with headache and loss of consciousness. Somnolence, GCS of 8 with withdrawal of limbs in response to pain were found without motor deficit. Bilateral flexor plantar cutaneous reflex was present. Divergence eye movement to convergence stimuli was detected after 24 hours.
Imaging Findings
Computed Tomography (CT) of the brain usually reveals a hypodense bilateral image in the paramedian thalamic region, without enhancement after IV contrast injection. This hypodense lesion usually appears after 6 hours and typically indicates irreversible ischaemic brain damage. In the first hours a normal CT might be found, however, it does not exclude the presence of acute ischaemia.
Conventional Magnetic Resonance Imaging (MRI) revealed an area of high T2 and FLAIR signal with restricted diffusion involving the paramedian territory of both thalamic nuclei. No enhancement was noted after gadolinium IV administration.
Discussion
Symmetrical and bilateral ischaemic brain lesions are an uncommon finding in clinical practice due to the anatomic features of brain blood supply. One of these types of lesions is bithalamic ischaemia, which can be explained by the presence of an anatomic variant of the paramedian arteries "The artery of Percheron" [1, 2].

The thalamus is one of the brain structures that show a great variety and complexity in its blood supply. Multiple small terminal vessels, branches of the posterior communicating artery and P1 and P2 segments of the posterior cerebral arteries, guarantee the blood supply to the thalamus [1, 2, 3].

The arterial supply of the normal thalamus can be mainly divided into four territories (anterior, paramedian, inferolateral and posterior). The paramedian territory usually shows a unilateral and ipsilateral arterial supply, but anomalous variations of the posterior circulation of brain do exist and bilateral or contralateral thalamic blood supply can be present [1, 2, 4, 5].

Three principal variants of the origin of the paramedian artery have been described (Frenchman, G Percheron), Figure 1:
- Type 1: Bilateral and symmetric origin of the paramedian arteries, arising from the
posterior communicating artery on each side (most common).
- Type 2: All the paramedian arteries are branches of the same posterior communicating
artery (on the left or right side). This type can be divided in:
2a: All paramedian arteries are independent branches of the same communicating
artery.
2b: All paramedian arteries are branches of a single unilateral arterial common trunk
and supply the medial thalamus bilaterally (known as the Percheron artery).
- Type 3: Both posterior communicating arteries form an arc from which the paramedian arteries arise to the right and left side. [1, 2, 6]

Occlusion of the common trunk in type 2b results in bilaterally symmetrical infarcts affecting the paramedian portions of the thalamus and brainstem. This condition is recognized with a typical finding on CT and MRI [1, 3, 5, 6].
Differential Diagnosis List
Bilateral thalamic infarcts, due to occlusion of artery of Percheron.
Deep cerebral venous thrombosis.
Infiltrative neoplasm
Variant of Creutzfeldt-Jakob disease
Final Diagnosis
Bilateral thalamic infarcts, due to occlusion of artery of Percheron.
Case information
URL: https://www.eurorad.org/case/12477
DOI: 10.1594/EURORAD/CASE.12477
ISSN: 1563-4086
Figure 1

Main anatomical variants of paramedian arteries.

Main anatomical variants of paramedian arteries.
Main anatomical variants of paramedian arteries.
Figure 2

Conventional non-contrast CT

Conventional non-contrast CT
Conventional CT showing a small symmetrical hypodense area in both paramedian thalamic regions (arrowheads). Calcification of pineal gland and right choroid plexus is detected as incidental finding (arrows).
Figure 3

Sagittal MRI T1

Sagittal MRI T1
Non-contrast sagittal T1-weighted images show a hypointense lesion in the territory of paramedian thalamus (arrow).
Figure 4

Axial MRI T2

Axial MRI T2
Axial T2-weighted images showing a bilateral and focal hyperintense lesion involving the paramedial territory of both thalami (arrows).
Figure 5

Axial MRI T2 FLAIR

Axial MRI T2 FLAIR
Axial FLAIR images demonstrating hyperintense signal area in bilateral thalamus (arrows).
Figure 6

DWI b1000 + ADC

DWI b1000 + ADC
A: Diffusion-weighted axial images demonstrate a hyperintense signal in bilateral thalamus corresponding to areas of infarct. B: The Axial ADC map shows decreased signal in bilateral thalamus (Restricted diffusion).
Figure 7

Axial non-contrast CT

Axial non-contrast CT
Non-contrast CT performed one year later. Axial image showing bilateral thalamic chronic infarctions, characterized by marked hypodensity and lack of mass effect (arrows).
Figure 8

Axial T2 TSE

Axial T2 TSE
Axial T2 weighted image (one year later). Hyperintense bilateral lesions with signal similar to cerebrospinal fluid (CSF), corresponding to the territory of previous bilateral thalamic infarcts (arrows).