subacute sclerosing panencephalitis ( sspe ) is a progressive inflammatory and degenerative disease of central nervous system caused by persistent infection of immune - resistant measles virus . the average period between exposure and onset of sspe ranges between 7 and 12 years . the typical clinical course of sspe is characterized with intellectual deterioration , personality and behavioral changes , myoclonic jerks , and sometimes pyramidal and extrapyramidal symptoms . however , in about 10% of patients clinical manifestations of sspe are not typical and that may cause a delay in the diagnosis and treatment of the disease . here , we report a case of sspe presenting with atypical clinical signs as loss of consciousness and gait instability . we report this patient in order to emphasize the importance of serial electroencephalogram ( eeg ) in sspe diagnosis and to remind sspe with atypical course . a 14-year - old boy was referred to us with loss of consciousness and gait instability . there was fatigue and decreased consciousness for 2 days and loss of consciousness in the last 24 h. there was no fever and vomiting . he was confused and responding to verbal stimulus with nonspecific sounds and withdrawing in response to pain . serologies for epstein - barr virus , cytomegalovirus , herpes simplex virus , and mycoplasma were negative . the eeg showed irregular activity with generalized slow waves and cerebral magnetic resonance imaging ( mri ) showed asymmetrical nonspecific signals on basal ganglia [ figure 1 ] . cerebrospinal fluid ( csf ) examination showed no cells , and normal protein ( 35 mg / dl ) and glucose ( 68 mg / dl ) . axial t2-weighted and flair mri showed asymmetrical nonspecific signals on basal ganglia meningoencephalitis and acute disseminated encephalomyelitis ( adem ) were suspected with present clinical and laboratory findings and he was treated with intravenous acyclovir initially . also , intravenous immunoglobulin ( ivig ) 400 mg/ kg / d for 5 days were administered because of the cerebral mri findings which might be compatible with adem . his second eeg revealed periodical generalized high - voltage slow wave complexes discharges that did not disappear with diazepam induction so that sspe was considered . the diagnosis of sspe was suspected and csf total and measles igg index , and csf oligoclonal bands were detected . increased titers of measles antibody in serum ( 1/256 ) and csf ( 1/8 ) ( normal : 1/4 or lower ) were found by complement fixation test . these results confirmed the diagnosis of sspe , and treatment with isoprinosine ( 100 mg/ kg / day ) was administered . he is in follow - up for 6 months without any abnormal clinical findings except minimal personality changes . the characteristic initial clinical signs of sspe are personality and behavioral changes and myoclonic jerks . sspe can also present with unusual features like generalized convulsions , loss of consciousness , acute - subacute coma , visual loss , ataxia , and hemiparesis . to date , in the literature many cases of sspe have been reported with atypical features.[35 ] the patient described here manifested atypical clinical findings and initially the diagnosis of sspe was not considered . unlike previously reported cases with fulminant presentation , we could achieve remission in our patient with ivig and isoprinosine . periodical high - amplitude slow wave complexes which can not be suppressed with diazepam is a characteristic eeg sign of sspe . although periodical complexes are usually generalized and may be detected at the onset of the disease , they may rarely be focal and unilateral . reported that a 14-month - old girl was admitted with hemiparesis and focal convulsion , and they confirmed the sspe diagnosis only after a long - term follow- up and periodical high - amplitude slow wave complexes detected on serial eegs . similarly , our patient was admitted with atypical clinical presentation and eeg findings were normal at the onset but there were periodical generalized high - voltage slow wave complexes that can not be suppressed with diazepam on 7 day eeg . so we suspected sspe , and high serum and csf measles antibody titers confirmed the diagnosis . that is why when a patient with a primary measles infection in history admitted with atypical clinical signs did not respond to treatment , and eeg should be evaluated carefully . serial eegs and lumbar puncture for csf measles antibodies should be considered to rule out sspe . mri is the best radiological imaging method for sspe . generally , mri is normal at the onset of the disease . cerebral atrophy and ventricular enlargement may also be seen on mri , but none of these findings are specific for sspe . reported that in some of the patients despite severe clinical course , mri are normal . so that they concluded that there is no correlation between mri and clinical course . the reported patients were managed as adem because of the periventricular white matter involvement in cerebral mri . reported that basal ganglia involvement is not infrequent in sspe . on admission , cerebral mr t2a and flair images of our patient showed nonspecific hyperintense asymmetrical lesions on basal ganglia . ivig , alfa interferon , ribavirin , steroids , and plasmapheresis have also been reported to be effective in sspe treatment . these drugs can not supply cure , they only slow the disease progression or prolong survival . prashanth and gurer reported that temporary remission could be rarely seen with isoprinosine and ivig in patients with sspe . he is in follow - up for 6 months without any abnormal clinical signs and symptoms except minimal personality changes . also , we think that our patient is in temporary remission . as a result , sspe is still an important medical problem in the developing countries . so sspe should be considered when a patient with measles history is admitted because of atypical clinical features like loss of consciousness , acute partial - generalized convulsion , acute - subacute coma , visual loss , ataxia , and hemiparesis . eeg of these patients should be evaluated carefully and serial eegs with diazepam should be performed in sspe - suspected cases . despite these surveys if sspe can not be ruled out , serum and csf measles antibodies should be examined .