A Case of Subacute Sclerosing Panencephalitis: Some Unusual Clinico-Radiological Manifestations
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.329564
Source of Support: None, Conflict of Interest: None
Subacute sclerosing panencephalitis (SSPE) is a late and universally fatal complication of measles infection. Typical presentations of SSPE are cognitive impairment, stereotyped myoclonus, seizures, and characteristic periodic discharges in the electroencephalogram. We report a case of SSPE with some unusual clinical and imaging features.
A 17-year-boy presented with recurrent seizures, abnormal postures of arms and legs for the last 3 years. On inquiry, parents told that his scholastic performance started declining five years back. They also noticed sudden jerky movements of limbs and trunk for the last three years. Sometimes, these jerky movements were associated with falls. His behavior started changing and his interest in day-to-day activities slowly declined. He is completely dependent on family members for the last two years. He has seizures with a frequency of 1–2 episodes per month. Parents also noticed abnormal posturing of all four limbs. They also noticed some abnormal involuntary chewing movements with grinding of teeth associated with typical sounds while fully awake [Video 1]. They used to subside spontaneously in a few minutes. These movements were not present during sleep. He had a history of measles at the age of 1 year. There is no history of measles immunization. On examination, he was conscious but not communicative. Cranial nerves are normal. The tone in all four limbs was markedly increased. There was dystonic posturing of all four limbs characterized by flexion at elbows, wrists, hips, and knees along with plantar flexion at ankles [Figure 1]. Deep tendon reflexes were brisk. Bilateral planters were not elicitable. His routine hematology and chemistry investigations were normal. Cranial magnetic resonance imaging showed extensive brain atrophy [Figure 2]a. A hot cross bun sign was observed in the mid-pontine region [Figure 2]b. Molar tooth sign was also evident at ponto-mesencephalic junction [Figure 2]c. His serum and cerebrospinal fluid were positive for IgG anti-measles antibodies. Electroencephalography revealed periodic complexes [Figure 3]. For seizures, the patient was receiving valproic acid and clonazepam.
Our patient had many unusual clinical and imaging features such as bruxism, generalized dystonia, and atypical MRI findings.
Bruxism is defined as a repetitive jaw-muscle activity characterized by clenching or grinding of the teeth. It is further divided into sleep bruxism and awake bruxism. Sleep bruxism is a common and benign condition. It is generally considered as a sleep-related rhythmic masticatory activity. Awake bruxism is less common but almost always associated with neurological disorders. It has been described in association with oromandibular dystonia, Alzheimer's disease, frontotemporal dementia, stroke, Parkinson's disease, normal pressure hydrocephalus, cerebellar hemorrhage, brainstem lesions due to Whipple's disease, temporomandibular joint disorders, anxiety, stress and following use of neuroleptics, amphetamine, and levodopa. Awake bruxism is frequently associated with oromandibular dystonia., Its pathophysiology is not clearly understood. In animal studies, stimulation of limbic structures such as the amygdala, the lateral hypothalamic area, or the jaw area of the motor cortex produced the grinding movement of the jaw. It is postulated that bruxism results from a loss of cortical inhibition. It is also hypothesized that there is a “bruxism generator complex” comprising a neuronal circuit that connects thalamus, subthalamus, striatum, and cerebral cortex. Any disruption in this neuronal circuit can cause loss of cortical inhibition on the trigeminal motor nuclei located in the pons and lead to bruxism.
SSPE involves both gray and white matter of the brain. In SSPE, brain involvement may have different patterns. Commonly, it starts in bilateral parieto-occipital regions and subsequently affects diffusely, and in late stages, have diffuse brain atrophy. Less commonly brain involvement can be focal and asymmetrical and can cause atypical manifestations. Hot cross bun sign is seen as cruciform hyperintensity in axial sections of pons on T2-weighted MRI. This sign represents the selective involvement of transverse pontocerebellar fibers. In SSPE, this sign, probably, suggests preferential involvement of transverse pontocerebellar fibers when the disease process involves the brainstem. It is most commonly found in multiple system atrophy, but this can also be seen in spinocerebellar ataxia, progressive multifocal leukoencephalopathy, variant Creutzfeldt-Jakob disease, parkinsonism secondary to presumed vasculitis and cerebrotendinous xanthomatosis and leptomeningeal metastases of breast cancer.
Dystonia is an unusual manifestation of SSPE. Dystonia in SSPE is, possibly, because of marked basal ganglia atrophy. Apart from atrophy of basal ganglia, atrophy of vermis and cerebellothalamic tracts in the superior cerebellar peduncle gave the visual appearance of molar tooth sign. Molar tooth sign is commonly described in Joubert syndrome where it occurs due to hypoplasia of vermis and lack of normal decussation of superior cerebellar peduncular fiber tracts.
It has been demonstrated that a decrease in cerebellothalamic connectivity leads to increased motor activation which may further cause dystonia.
SSPE can be prevented by employing effective immunization with measles vaccine. In developed countries, due to proper immunization, the occurrence of measles is rare and its late complications are even rarer. In developing countries like India, measles is still prevalent due to poor coverage of vaccination mainly due to ignorance and misconception regarding the measles vaccine. SSPE is still a clinical problem in developing countries.
In conclusion, in countries where SSPE is still encountered in large numbers, a physician should be cautious about unusual manifestations.,
The patient's family has given consent for documentation and publication of the patient's clinical details, photographs, and videos in a medical journal.
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There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]