Images in Neurology

Hot cross bun sign in HIV‑related progressive multifocal leukoencephalopathy Sandeep Padmanabhan, Ajith Cherian, Thomas Iype, Mini Mathew1, Sony Smitha Department of Neurology, Government Medical College, 1Consultant Ophthalmologist, Rose Eye Clinic, Vellayambalam, Trivandrum, Kerala, India For correspondence: Dr. Ajith Cherian, Department of Neurology, Government Medical College, Trivandrum, Kerala, India.

E‑mail: [email protected]

Ann Indian Acad Neurol 2013;16:672-3

Introduction Hot cross bun (HCB) sign is a cruciate hyperintensity in the pons best seen on axial T2‑weighted and fluid attenuation inversion recovery (FLAIR) sequences of magnetic resonance imaging (MRI) of the brain. This sign is classically described in degenerative diseases like multiple system atrophy (MSA) and rarely with infectious diseases of the central nervous system. We report here, HCB sign in a patient of human immunodeficiency virus (HIV)‑related progressive multifocal leukoencephalopathy (PML).

asymmetrical T2 hyperintense lesions involving the left middle and inferior cerebellar peducle extending into left cerebellar hemisphere with atrophy of the same structures [Figure 1]. The left cerebellar hemispheric hyperintensities were partially suppressible on FLAIR and not enhancing on contrast [Figure 2]. Magnetic resonance spectroscopy revealed reduction of N‑Acetylaspartic acid peak with mild elevation of choline. Imaging features suggested a possible necrotic demyelinating process asymmetrically, involving the left cerebellar white matter and transverse pontine fibers consistent with PML.



A 37‑year‑old lady presented to us with subacute onset progressive ataxia, with tendency to sway toward the left, of 2 month duration. She had significant weight loss, anorexia, and recurrent fevers for 6 months. She was emaciated, had oral candidiasis, and hepatomegaly. Neurological examination revealed left gaze evoked nystagmus, incoordination involving the left extremities, and slurred speech. HIV serology done was positive with a CD4 count of 28/µL. Cerebrospinal fluid study revealed normal opening pressure, mild elevation of protein (65 mg%) with no cells and normal glucose.

The cruciform hyperintensity seen in pons resembles a HCB Table 1: Conditions where ‘‘hot cross bun sign’’ in pons is described in literature Multiple system atrophy‑cerebellar type (MSA‑c)[2] Spinocerebellar Ataxia 2 (SCA 2)[3] Machado‑Joseph disease (SCA 3)[3] Variant Creutzfeldt‑Jacob disease (vCJD)[4] HIV‑related progressive multifocal leukoencephalopathy (PML)[6] Secondary parkinsonism (due to presumed vasculitis)[5]

MRI of the brain multiplanar T1, T2, FLAIR, diffusion and postcontrast done on a 1.5 Tesla system (Avanto‑SQ Engine, Siemens Medical Systems, Erlanger, Germany) revealed the classical HCB sign in pons. In addition, there were Access this article online Quick Response Code:


a DOI: 10.4103/0972-2327.120479



Figure  1: Axial T2  (a) and fluid attenuation inversion recovery (b) showing “hot cross bun” appearance with cruciate T2 hyperintensity in the pons (arrow). Postcontrast T1 axial (c) showing no enhancement. Inset shows top view of hot cross bun

Annals of Indian Academy of Neurology, October-December 2013, Vol 16, Issue 4

Sandeep, et al.: Hot cross bun sign in PML


Table 2: Points to differentiate progressive multifocal leukoencephalopathy from multiple system atrophy and spinocerebellar ataxias (SCA 2 and 3) on magnetic resonance imaging despite the presence of “Hot cross bun” sign Differentiating points on MR imaging

Infectious causes like PML


Spinocerebellar ataxias (SCA 2 and 3)

Hyperintensities of the MCPs and cerebellar hemispheres

Asymmetric hyperintensities of the MCPs and cerebellar hemispheres depending on extent of viral involvement Asymmetric atrophy of the cerebellar hemispheres and MCPs depending on extent of viral involvement

Symmetric hyperintensities of the MCPs are usually more pronounced than cerebellar hemispheric hyperintensities[1] Symmetric atrophy of the cerebellar hemispheres (in 66% of patients with MSA on 1.5 T scans), MCPs (47%), pons (38%)[1]

Not described

Necrotic demyelinating process leads to encephalomalacia changes and such T2 hyperintense signals due to presence of fluid is partially suppressed on FLAIR images Not described

Not described

Atrophy of the cerebellum and MCPs

Presence of encephalomalacia changes

MR imaging changes in basal ganglia especially putamen

Contrast enhancement

Described in the presence of IRIS

Hyperintense rim at the lateral putaminal edge (41%) patients with MSA on 1.5 T scans) and putaminal atrophy. Relative putaminal hypointensity on 1.5 T scans tended to be more frequent in patients with MSA (28.1%).[1] Not described

Symmetric atrophy of cerebellum prominent in both SCA 2 and 3. Superior cerebellar peduncle atrophy is a characteristic feature of SCA‑3[7] Not described

Caudate and putamen atrophy prominent in SCA‑3. No hyperintensities in basal ganglia.[7]

Not described

FLAIR=Fluid attenuation inversion recovery, IRIS=Immune reconstitution inflammatory syndrome, MCPs=Middle cerebellar peduncles, MR=Magnetic resonance, MSA=Multiple system atrophy, PML=Progressive multifocal leukoencephalopathy, T=Tesla, SCA=Spinocerebellar ataxia





Figure 2: Axial T2 (a) showing asymmetrical T2 hyperintensity involving the middle cerebellar peduncle extending to the left cerebellar hemisphere, partially suppressed on fluid attenuation inversion recovery (b) with no contrast enhancement (c) Note the asymmetric atrophy involving the left cerebellar hemisphere

baked for the last Thursday before Easter and hence called so. The sign is due to a selective loss of myelinated transverse pontocerebellar fibers and neurons in the pontine raphe with preservation of the pontine tegmentum and corticospinal tracts.[1] It is most often seen in cerebellar type of MSA.[2] HCB sign has also been reported in spinocerebellar ataxia  (SCA) and variant Creutzfeldt–Jakob disease.[3,4] Muqit et al.,[5] in 2001 described a patient with parkinsonism due to presumed vasculitis with HCB sign on MRI. HCB sign has been reported in two patients with HIV‑related PML from India by Yadav et al.,[6] [Table 1]. The HCB appearance in PML is probably due to the damage and subsequent gliosis of the cerebellar connections and pontocerebellar fibers in the pons due to viral infection  [Table  2]  (Lists imaging differentiating features of PML from MSA and SCA). To date, ours is the world’s second report of a patient with HIV‑related PML with HCB sign on MRI.

1. Schrag A, Kingsley D, Phatouros C, Mathias CJ, Lees AJ, Daniel SE, et al. Clinical usefulness of magnetic resonance imaging in multiple system atrophy. J Neurol Neurosurg Psychiatry 1998;65:65‑71. 2. Savoiardo M, Strada L, Girotti F, Zimmerman RA, Grisoli M, Testa D, et al. Olivopontocerebellar atrophy: MR diagnosis and relationship to multiple system atrophy. Radiology 1990;174:693‑6. 3. Lee YC, Liu CS, Wu HM, Wang PS, Chang MH, Soong BW. The ‘hot cross bun’ sign in the patients with spinocerebellar ataxia. Eur J Neurol 2009;16:513‑6. 4. Soares‑Fernandes JP, Ribeiro M, Machado A. “Hot cross bun” sign in variant Creutzfeldt‑Jakob disease. AJNR Am J Neuroradiol 2009;30:E37. 5. Muqit MM, Mort D, Miskiel KA, Shakir RA. “Hot cross bun” sign in a patient with parkinsonism secondary to presumed vasculitis. J Neurol Neurosurg Psychiatry 2001;71:565‑6. 6. Yadav R, Ramdas M, Karthik N, Kulkarni GB, Dawn R, Kumar MV, et al. “Hot cross bun” sign in HIV‑related progressive multifocal leukoencephalopathy. Neurol India 2011;59:293‑4. 7. Klockgether T, Skalej M, Wedekind D, Luft AR, Welte D, Schulz JB, et al. Autosomal dominant cerebellar ataxia type I. MRI‑based volumetry of posterior fossa structures and basal ganglia in spinocerebellar ataxia types 1, 2 and 3. Brain 1998;121:1687‑93. How to cite this article: Padmanabhan S, Cherian A, Iype T, Mathew M, Smitha S. Hot cross bun sign in HIV-related progressive multifocal leukoencephalopathy. Ann Indian Acad Neurol 2013;16:672-3. Received: 10‑05‑13, Revised: 23‑06‑13, Accepted: 05‑07‑13 Source of Support: Nil, Conflict of Interest: Nil

Annals of Indian Academy of Neurology, October-December 2013, Vol 16, Issue 4

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