LETTERS TO THE EDITOR
|Year : 2022 | Volume
| Issue : 6 | Page : 1252-1254
Subacute sclerosing panencephalitis: A name with many faces
Ayush Agarwal1, Divyani Garg2, Kamlesh Tayade1, Abhishek Vaigankar1, Kanukuntla Saikrishna1, Pooja Anand1, Vinay Goel3, Divya M Radhakrishna1, Ajay Garg3, Achal K Srivastava1
1 Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Neurology, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India
3 Department of Neuroradiology, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||02-Oct-2022|
|Date of Decision||10-Nov-2022|
|Date of Acceptance||11-Nov-2022|
|Date of Web Publication||23-Nov-2022|
Department of Neurology, All India Institute of Medical Sciences, New
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Agarwal A, Garg D, Tayade K, Vaigankar A, Saikrishna K, Anand P, Goel V, Radhakrishna DM, Garg A, Srivastava AK. Subacute sclerosing panencephalitis: A name with many faces. Ann Indian Acad Neurol 2022;25:1252-4
|How to cite this URL:|
Agarwal A, Garg D, Tayade K, Vaigankar A, Saikrishna K, Anand P, Goel V, Radhakrishna DM, Garg A, Srivastava AK. Subacute sclerosing panencephalitis: A name with many faces. Ann Indian Acad Neurol [serial online] 2022 [cited 2023 Jan 29];25:1252-4. Available from: https://www.annalsofian.org/text.asp?2022/25/6/1252/361870
Subacute sclerosing panencephalitis (SSPE) is a slow virus disease. It is a rare complication that occurs because of persistent measles infection, typically presenting with progressive cognitive impairment and myoclonus between 8 and 11 years of age. SSPE is invariably fatal within 3–5 years of onset, although treatment may occasionally lead to disease stabilization. Vaccination against measles is protective against the development of SSPE. Between 4 and 11 per 100,000 cases of measles progress to SSPE. Although the combination of progressive cognitive impairment with myoclonus in a young individual is well established as a hallmark presenting feature, atypical presentations have been reported not infrequently and include isolated extrapyramidal syndrome, drug refractory epilepsy, and psychiatric symptoms alone. In this sense, SSPE probably deserves a place as one of the great mimics in neurology. We present a series of rarer and atypical presentations of SSPE that emphasize these very masquerading qualities. These include presentations with Gerstmann syndrome, cognitive impairment alone in young adulthood, new onset status epilepticus, ataxia, and Rasmussen's encephalitis (RE)-like illness [Supplementary Table 1].
The prevalence of SSPE has decreased since the introduction of measles vaccination in the immunization program of most countries but continues to be high in the developing world. Vaccine hesitancy in the developed world has led to a recent resurgence of SSPE. It was earlier diagnosed by the Dyken's criteria (3/5 should be present): subacute progressive cognitive impairment with myoclonus, electroencephalography (EEG) showing periodic high amplitude discharges, cerebrospinal fluid (CSF) hypergammaglobulinemia or presence of oligoclonal bands, presence of anti-measles antibodies in serum and CSF, and brain biopsy revealing panencephalitis. However, this was modified in 2010 due to atypical presentations, and now two major and one minor criterion are required for diagnosis [Supplementary Table 2].
Gerstmann syndrome is a constellation of dyscalculia, dysgraphia, left-right confusion, and finger agnosia. Isolated agraphia and finger agnosia are called cardinal symptoms and the others are associated features. The typical localization involves the left angular gyrus. It has not been described as a presenting feature of SSPE so far. Balint syndrome has been described in SSPE., Its exact pathophysiology is not well elucidated and may be explained by anatomical proximity of multiple neuronal networks or due to a single neuronal network which is responsible for mediating these deficits. This case illustrates that a typical constellation of cortical features in the form of Gerstmann syndrome may be a presenting feature of SSPE, even prior to the onset of myoclonus. Hence, the subacute development of a cortical syndrome in a young individual must raise the possibility of SSPE in the diagnostic algorithm.
One of our patients presented with progressive cognitive and behavioral impairment in the absence of myoclonic jerks or periodic discharges on EEG. Although these findings are typical in advanced SSPE, the complete absence of myoclonic jerks throughout the illness, presentation in the third decade, absence of characteristic imaging and EEG findings were unusual. Chakor and Santosh published a series of four cases of SSPE that presented with rapidly progressive dementia in young adults aged between 18 and 23 years. One of their cases had no periodic complexes as well. Nair et al. similarly described SSPE causing cognitive impairment alone in a 35-year-old man without myoclonic jerks and periodic discharges on EEG. Myoclonic jerks have been described in 23%–64% of SSPE patients and usually occur in Jabbour's SSPE stage II. These stages are not well defined in adults and might explain the absence of myoclonus in our patients.
RE is a rare and chronic neurological disorder characterized by progressive neurological deficits and drug refractory epilepsy. It usually affects children and young adults, and the diagnosis is predominantly clinicoradiological. SSPE was described to mimic RE in one case previously. Our patient fulfilled the diagnostic criteria of RE but was diagnosed as SSPE, emphasizing this rare presentation. Atypical features included presentation as SSPE, later age of onset, and absence of periodic discharges. A distinguishing feature from RE could be the absence of its sine qua non feature, that is, epilepsia partialis continua (EPC) in SSPE patients. Rare SSPE cases with EPC have been described. However, these children did not have imaging findings suggestive of RE.
Status epilepticus as a heralding manifestation of SSPE has been rarely reported. We could find one previously published case presenting with convulsive status epilepticus. Singhi et al. described two children with SSPE presenting with non-convulsive status epilepticus (NCSE). Disease progression may cause transient NCSE-like EEG discharges or lead to shortening between the interval of periodic discharges, culminating in continuous slow wave activity. Our patient probably decompensated following a super-added infection and improved with management of status epilepticus.
SSPE patients presenting with pure cerebellar ataxia have been described infrequently. Rajper et al. and Wölfle et al., previously described SSPE presenting with subacute ataxia in a 7- and 8-year-old child, respectively. All other cases in literature had other neurological deficits along with ataxia at presentation. However, our patient presented with a chronic progressive pancerebellar syndrome and eventually developed concomitant cognitive impairment. History of parental consanguinity provoked a diagnostic odyssey, with extensive evaluation for suspected autosomal recessive cerebellar ataxic syndrome.
|Figure 1: Axial FLAIR (a) and Coronal T2-W (b) images show sulcal hyperintensity of the right superior frontal lobe with an asymmetrical atrophy of the bilateral frontal lobe (left and right). Follow-up CT scan (c) shows the progression of cerebral atrophy. After three months, in repeat MRI, axial FLAIR image (d) shows new areas of gyral hyperintensity in the bilateral superior frontal lobes, right postcentral gyrus, and bilateral posterior cingulate cortex. Leptomeningeal enhancement along bilateral parietal lobes (right and left) is seen in post-contrast axial T1-W image (e). Follow-up MRI axial and coronal image (f and g) after three months show new areas of cortical and subcortical white matter hyperintensity in the bilateral cerebral hemisphere with the progression of cerebral atrophy. Similar findings can also be seen in CT (h)|
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Overt measles infection did not occur in most of our patients (mild or asymptomatic infection may have been missed). However, none of our patients were vaccinated against measles. Thus, vaccination against measles is not only paramount but a history of non-vaccination may be a better surrogate risk marker compared to a history suggestive of measles infection.
The diagnosis of SSPE was confirmed in all cases by elevated anti-measles antibody levels in serum and CSF, which have high sensitivity, specificity and positive predictive value. Early diagnosis is important as a combination of intrathecal interferon and oral isoprinosine can then be effective in up to 30%–35% cases.
SSPE may be the great masquerader of the present era and should always be considered as a differential in all young individuals presenting with acquired neurological deficits. Vital clues may be obtained from EEG, which must be considered early during evaluation of atypical neurological syndromes in young patients. The present case series serves to highlight rarer presenting manifestations of SSPE.
Declaration of patient consent
Written and informed consent was taken from the patient or caregivers.
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Conflicts of interest
There are no conflicts of interest.
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