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systemic dehydration and diffuse central nervous system ( cns ) signs without any other illness is referred to as dehydration encephalopathy ( de ) , with disturbed consciousness being the main clinical feature .
herein we investigate the incidence of de among persons with disturbed consciousness of various etiologies who visited the emergency unit at our university hospital .
we reviewed the emergency medical case records during a 6-month period ( from january to june , 2010 ) . among them , 132 patients presented with disturbed consciousness as the sole initial manifestation on arrival .
they were 75 men , 47 women ; mean age 68 years ( 1695 years ) ; 126 arriving by ambulance , 6 by car .
we performed the initial work - up including physical / neurological examination , blood test and urine analysis , drug intoxication screening , cerebrospinal fluid examination , electrocardiography , head - up tilt test , chest x - ray , chest and abdominal ct , brain magnetic resonance imaging ( mri ) including diffusion- weighted images , carotid ultrasonography , and electroencephalography , in order to determine the diagnosis to the extent possible . among these ,
the inclusion diagnostic criteria of de were i ) acute diffuse cns signs on arrival that were ameliorated at discharge , after receiving 5001000 ml intravenous saline infusion on admission day , and ii ) systemic findings ( dry skin , etc . ) and blood test results ( increased total protein , blood urea nitrogen , etc . ) suggesting dehydration on arrival , which were reversed at discharge after saline infusion .
the exclusion criteria of de were i ) diffuse cns diseases such as encephalitis or systemic diseases ( hypoxia , hyperglycemic coma , extreme hypertension , etc . ) , ii ) drug abuse , and iii ) focal cns diseases such as stroke , etc .
the present study was approved by the ethics committee in sakura medical center , toho university .
the underlying diseases in 132 patients presented with disturbed consciousness as the sole initial manifestation on arrival were found to be as follows : syncope ( 30% ) , drug intoxication ( 11% ) , hypoglycemia ( 10% ) , epilepsy ( 9% , excluding de cases ) , stroke ( bleeding ) ( 8% ) , infection ( 8% ) , alcohol intoxication ( 6% ) , psychiatric diseases ( 3% ) , stroke ( infarction ) ( 3% ) , de ( 2% ) , uremia / hepatic encephalopathy ( 2% ) , and others ( 4% ) ( figure 1 ) .
the de cases were uniformly elderly ( age more than 68 years ) ; all had the same clinical features , described below , and were soon completely restored to normal .
after carefully excluding other etiologies , the incidence of de was 2% among all persons in the emergency unit and 4% among persons older than 68 years . 

figure 1incidence of dehydration encephalopathy and other etiologies among patients with disturbed consciousness . after carefully excluding other etiologies ,
after carefully excluding other etiologies , dehydration encephalopathy comprised 2% of disturbed consciousness at the hospital emergency unit .
de was originally described as an emergency by physicians in our neurology department . in that study ,
clinical features were summarized as follows : elderly ( mean age , 80 years ) and having underlying brain disease , e.g. , ischemic white matter lesions , etc .
in addition , many showed frontal hypoperfusion in single - photon computed tomography ( spect ) and high - amplitude slow waves in electroencephalography ( eeg ) . provoking events in
they typically showed acute presentation of diffuse cns signs ( consciousness disturbance in most , new onset of epilepsy in some ) and achieved complete recovery quickly ( mean period 4 days ) .
the results of the present study showed that the incidence of de in emergency units is not likely to be common ; nevertheless , awareness of de is extremely important in order to avoid unnecessary medication in elderly subjects .
in addition , the results of the present study help in the differential diagnosis of de and other neurologic / systemic diseases that potentially cause disturbed consciousness as the sole initial manifestation .
systemic dehydration and diffuse central nervous system signs without any other illness is referred to as dehydration encephalopathy ( de ) . however , the incidence of de at emergency units remains uncertain . 
 we investigated the incidence of de among persons with disturbed consciousness who visited the emergency unit . 
 we reviewed the medical case records of the emergency unit at our university hospital during a 6-month period . among them , 132 patients presented with disturbed consciousness as the sole initial manifestation on arrival . 
 they were 75 men , 47 women ; mean age 68 years ( 1695 years ) . 
 after carefully excluding other etiologies , the incidence of de was 2% among all persons in the emergency unit and 4% among persons older than 68 years . in conclusion , 
 the incidence of de in our emergency unit was not common . 
 nevertheless , recognition of de is extremely important in order to avoid unnecessary medication in elderly subjects .