A rare differential diagnosis of excessive daytime sleepiness -Artery of Percheron territory infarct

INTRODUCTION

We present a 56-year-old man who was admitted at Emergency Room of UniversityHospital of Universidade Federal de São Paulo with initial complaint ofexcessive daytime sleepiness (EDS), left-sided weakness and sudden onset memory lossbeginning 5 days ago. Symptoms started around 2pm, when he was found by his wife inthe bedroom, drowsy and unable to get up. He was right handed and previouslydiagnosed with arterial hypertension and hypercholesterolemia, regularly usinglosartan 50mg/day and simvastatin 20mg/day. There was no history of daytimesleepiness before this period. There was also no history of fever, headache,intoxication, head manipulation, trauma or neck pain.

At hospital admission, his blood pressure was 135x85mmHg and serum glucose was98mg/dl. Neurological examination showed a sleepy patient with Epworth SleepinessScale (ESS) of 14, dysarthria, motor function leftsided with grade 2/5 in upperextremities and 3/5 in lower extremities, and hypoesthesia in right side of body.Deep tendon reflexes on the left side were +3/4+ and a Babinski signal was found onthe same side. After that, he was immediately hospitalized for clinical treatmentand complementary investigation.

A brain computed tomography (CT) scan was performed one and a half hour afteradmission and showed a right thalamocapsular region infarct. Brain magneticresonance imaging (MRI) was performed the day after the admission showing paramedianthalamic hyperintensity (Figure 1) and rostralmidbrain hyperintensity extending along the pial surface of the midbrain of theinterpeduncular fossa, characterizing the “V” sign (Figure 2) on FLAIR and T2-weighted images.

Figure 1

Axial FLAIR (A) and coronal T2-weighted (B) brain MRI showing withparamedian thalamic hyperintensity (arrows).

Figure 2

Axial FLAIR brain MRI showing rostral midbrain infarct (A) and a Vshapedhyperintense signal intensity along the pial surface of the midbrain atthe interpeduncular fossa (the 'V' sign, indicated by arrow).

Currently, 4 weeks after symptoms onset, patient is accompanied at neurology clinicand does rehabilitation with physio and speech therapies. He presented improvementof motor function (grade 4/5 on both upper and lower left extremities) and EDS(ESS=8).

DISCUSSION

There are many causes of EDS. Sleep deprivation, sleep disorders, psychiatricdiseases, use of medications, circadian rhythm sleep-wake disorders, andneurological diseases are examples of differential diagnosis. Stroke is an exampleof neurological diseases that can commonly drives EDS, with high prevalence andenourmous impact in our society¹.

The overlap among stroke and sleep diseases is an authentic issue. Stroke patientshave higher prevalence of sleep diseases such obstructive sleep apnea, restless legsyndrome, and others. Unfortunately, the usual scales to identify the EDS in thispopulation are not useful. Systematic investigation can be done to identify sleepproblems².

On the other hand, acute lesions of CNS can develop EDS. Extensive strokes with brainedema can leave a brain herniation and coma. Other causes of EDS after stroke arestrategic lesions at thalamus and brainstein³. Artery of Percheron (AP) is an unusual anatomical variationthat originates from the posterior cerebral artery and irrigates the paramedianregions of the thalamus and part of the midbrain⁴. When this artery is occluded, usually by cardioemboliccause, there is a characteristic neuroimaging pattern: bilateral paramedian thalamicinfarctions with or without involvement of midbrain^5,6.

Interestingly, the obstruction of the AP cannot usually be seen by angiography. It isimportant clinical suspicions with detailed drowsy patient’s history. Awareness ofthe clinical and neuroimaging features of this stroke syndrome is essential fortimely diagnosis and appropriate management.

Patients with AP infarct classically have sleepiness, vertical gaze paresis andmemory impairment⁶. Sleep/wakedisturbances were observed in patients with AOP infarction from stroke onset orbecome evident following recovery from coma, however, a few clinical presentationswere described having EDS as initial complaint^3,7,8. Altered mental status can present anywhere on thespectrum from drowsiness or confusion to hypersomnolence or coma^6,8. These disorders of vigilance generally occur with sudden onsetand may persist until death, though cases of complete recovery have beendocumented^9,10. In our patient the EDS was very imperative asinitial complaint improving after few weeks.

Paramedian thalamic stroke due to AP infarct is a cause of organic hypersomnia, whichin the absence of systematic sleep-wake studies has been attributed to disruption ofascending activating impulses and considered a “dearoused” state¹¹. Bassetti et al.⁷ showed that paramedian thalamicstroke is accompanied not only by a dearousal but also a disruption of NREM sleep,which parallels the severity of hypersomnia. Hypocretin deficiency was not involvedin hypersomnia observed in patients after AP infarction¹².

Further studies are needed to explain pathophysiological mechanisms and therapeuticpossibilities involving patients with EDS following AP infarction, as well asfactors which contribute for their outcomes.