White Heart in Pons—A Rare Imaging Sign in Bilateral Pontine Infarction

An 89-year-old hypertensive male presented to a local hospital with a history of sudden onset dizziness and two episodes of vomiting after having dinner. On neurological examination, he was drowsy with mild weakness in all the four limbs. He progressively developed tetraplegia within 2 hours of admission and was immediately shifted to our tertiary care center in the emergency department, where he suddenly developed loss of consciousness. He became nonresponsive with a Glasgow coma scale (GCS) of E2V1M2. His plantar reflex was bilaterally extensor. He urgently required ventilator support. Routine biochemical tests including serum electrolytes, electrocardiogram, and transthoracic echocardiogram were within normal limits. Magnetic resonance imaging (MRI) brain was performed, which showed acute infarct in bilateral pons with characteristic white heart appearance on diffusion-weighted image (DWI), T2-weighted and fluid-attenuated inversion recovery (FLAIR) axial images ([Fig. 1]). Contrast-enhanced MRI (CEMRI) was also performed, which showed filling defect in midbasilar artery, suggestive of thrombus, resulting in near complete occlusion with posterior eccentric filling. There was normal opacification of distal basilar artery partially, because of retrograde flow from right posterior communicating (PCom) artery ([Fig. 2]). Mechanical thrombectomy was not offered in view of large volume infarct in pons. The patient died of cardiopulmonary complications on the second day of his admission.

Fig. 1 Magnetic resonance imaging (MRI) brain. (A, B) Diffusion- weighted image (DWI) and corresponding apparent diffusion coefficient (ADC) map show acute pontine infarct with a characteristic “heart appearance.” (C, D) Axial T2-weighted and fluid-attenuated inversion recovery (FLAIR) images show the same “heart-shaped” hyperintensity in pons.

Fig. 2 Contrast-enhanced magnetic resonance imaging (CEMRI) of brain (A, B) Sagittal and coronal T1-weighted, maximum intensity projection (MIP) images show basilar artery near complete occlusion (arrow). (C-G) Axial postcontrast images showing thrombus in basilar artery with thin eccentric filling of contrast (yellow arrows) and opacified basilar artery proximal and distal to it (red arrow).

The heart-shaped sign in medulla on MRI due to bilateral medial medullary infarction is uncommon, however many cases are featured in literature.[1] [2] The pattern of vascularization of pons is somewhat similar to that of medulla, and thus it may encounter similar heart-shaped appearance in pons also. However, white heart appearance on MRI in bilateral pontine infarction is extremely rare. To date, there are only four cases of white heart appearance in the pons on MRI axial images reported in the literature ([Table 1]).[3] [4] [5] [6] In addition to that, Kumral et al[7] mentioned 14 cases of bilateral anteromedial pontine infarcts, out of which 7 cases had the heart-shaped appearance, although they never mentioned this rare appearance. In most of the previously reported cases of heart-shaped appearance of pons, there was normal basilar artery on angiography[3] [5] [6] Venkatesan et al[4] also reported a case of heart-shaped infarct in pons due to underlying severe atherosclerotic changes in vertebral and basilar artery. This suggests the likely possibility of small artery disease or basilar artery atheroma as an etiology for white heart-shaped appearance of pontine infarct. The present case is another example of bilateral pontine infarction due to thrombus in basilar artery, resulting in near complete occlusion; however, the presence of associated underlying atherosclerotic disease cannot be ruled out, as the contrast angiography or digital subtraction angiography (DSA) was not done in our case. The blood supply to the pons from basilar artery is via threes branches and is depicted schematically in [Fig. 3]. The paramedian branches (7-10) supply the anteromedial pons; short circumferential branches (5-7) supply the anterolateral pons and the middle and superior cerebellar peduncles; and paired long circumferential branches (superior cerebellar and anterior inferior cerebellar arteries) supply the lateral territory.[3] [4] There should be bilateral involvement of the anteromedial and the anterolateral arterial territories, with sparing of the lateral territories to have the white heart appearance of infarct in the pons.

Table 1 Reported case of heart-shaped appearance of infarct in pons

Author's name (year)	Age/sex	Clinical presentation	Location of heart-shaped infarct	Angiography findings/CEMRI findings	Final outcome of the patient
Abbreviations: CEMRI, contrast-enhanced magnetic resonance imaging; DSA, digital subtraction angiography; MRA, magnetic resonance angiography.
Ishizawa et al[5]	87Y/M	Tetraparesis	Pons	Normal basilar artery on MRA	Tetraplegic
Venkatesan et al[4]	53Y/M	Vertigo, slurred speech, tetraplegia	Pons	Diffuse atherosclerotic disease of the vertebral and basilar arteries on MRA	Tetraplegic
Sen et al[3]	60Y/M	Dizziness, Unsteady gait, tetraparesis	Pons	Normal basilar artery on MRA	Died of cardiorespiratory complications
Zhou et al[6]	67/F	Vertigo, nausea, vomiting, dysarthria, bilateral facial weakness, tetraplegia	Pontomedullary junction	Normal basilar and vertebral artery on DSA	Tetraplegic (upper and lower limb with grade 2 power), dysarthria, bilateral facial weakness and nasal feeding
Present case	89Y/M	Vomiting, altered sensorium and tetraplegia	Pons	Near complete occlusion of basilar artery on CEMRI	Died of cardiopulmonary complications

Fig. 3 Schematic diagram showing three arterial territories of pons.

This characteristic appearance of white heart may also mimic pontine glioma and osmotic myelinolysis. Diffuse pontine glioma occurs in children, usually expands, and distorts the pons with no or minimal diffusion restriction on MRI. Osmotic myelinolysis presents with a history of rapid correction of hyponatremia, and it usually spares the periphery of the pons.[3] Overall outcome of bilateral pontine infarction is poor with severe morbidity and mortality ([Table 1]). Therefore, early clinical diagnosis and detection of subtle findings on MRI is critical in these cases, so that appropriate timely intervention can be offered to such patients.

Publication History

Article published online:
14 November 2021

• References

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