T
HE World Health Organisation defines Acute Encephalitis
Syndrome (AES) as a constellation of symptoms like acute
onset of fever and altered mental status—confusion, diso-
rientation, irritability and impaired speech with or with-
out seizures in a person of any age, occurring at any time
of the year. It can be caused by infection, inflammation or toxic
metabolic reasons, leading to affliction of the brain tissue.
Two medical terms need to be understood in this context:
encephalitis and encephalopathy. The former is almost always
accompanied by inflammation of the meninges (protective
tissues that cover the central nervous system). The latter is a
physiological derangement of brain function caused by metabo-
lic conditions: very low blood sugar level,
kidney or liver failure, disturbed fluid and
electrolyte balance, drugs or toxins like
lead, mercury, pesticides to food-related
toxins, like, possibly those in litchis.
The term AES collectively includes enc-
ephalitis as well as encephalopathy and
hence can have myriad causes. In most
AES cases, the cause is presumed to be
viral and is treated accordingly. The actual
identification of the causative agent is
difficult, as in around one-third patients,
no causative agents can be identified.
Encephalitis is more common in chil-
dren, affecting mostly those less than age
- It differs greatly in different reg ions
and in different seasons of the year. The
Japanese encephalitis outbreak was
the earliest identified etiological agent
in 1950s in India. Since then, multiple
agents have been identified causing
periodic outbreaks from time to time. The Chandipura Virus
has been reported from the Nagpur region of Maharashtra,
eastern Gujarat and Andhra Pradesh. Nipah Virus has been
reported from West Bengal and Kerala. The mite-borne Scrub
typhus has been found in up to 20 per cent of all AES cases in the
Gorakhpur region of Uttar Pradesh and about 14-60 per cent
elsewhere in the country. It is beco ming increasingly common
due to rapid urbanisation of rural areas. It has now been isolated
at various cities in Tamil Nadu, Uttarakhand and UP.
Toxin mediated encephalopathy has emerged as a major cause
affecting children in recent years. Encephalopathy linked to li-
tchis has been reported in epidemic forms in Muzaffarpur,
Bihar, and Malda, Bengal. Every year, during the harvest period
in the months of April-June, surge in deaths due to AES, pre-
dominantly in children has been observed. The victims are
usually malnourished children of lower socio-economic strata.
The toxins present in the fruit—hypoglycin-A and methylene
cyclopropyl glycine (MCPG)—result in severe fatty acid oxida-
tion inhibition and hypoglycaemia. They impair the energy
producing mechanisms in the body, leading to reduced blood
sugar. This in turn leads to reduced energy supply to the brain
and impaired brain functions, resulting in encephalopathy.
Malnourished children are highly vulnerable due to a reduced
store of energy. Two studies, so far, have found an association
with litchi consumption, prolonged fasting and malnutrition.
Between May 26, and July 17, 2014, 390 patients of AES were
admitted to the two referral hospitals in
Muzaffarpur of whom 31 per cent died. At
admission, 62 per cent had low blood
glucose concentration. Litchi consu-
mption, and missing of an evening meal in
the 24 hours before illness onset, were the
associated factors. About 90 per cent of
case-patient specimens had severe dis-
ruption of fatty acid metabolism. Early
identification and immediate treatment
of hypoglycemia may be the most crucial
step in the management of such cases.
Some of the causes of AES are self-
limiting, while others may rapidly lead to
death or severe neurological damage.
Mortality is mainly due to swelling and
inflammation that create severe pressure
around the brain and damage its vital
centres that control respiratory and cir-
culatory functions. Severe and sudden
AES leads to high mortality within 2-5
days and those surviving are usually left with residual neurolog-
ical deficits. In milder cases, patients can recover in 1-2 weeks.
Preventive measures are key to improving overall outcomes.
Vaccinations against JE, varicella, measles, mumps and rubella
virus have been widely successful in preventing outbreaks.
AIIMS, New Delhi, has set up a Centre of Excellence and
Advanced Research for Childhood Neurodevelopmental disor-
ders in the Child Neurology Division, Department of Pediatrics.
Of its various projects, one is dedicated to study comprehen-
sively etiological profile of AES, encephalopathy and encepha-
litis in infants, children and adolescents. O
(The author is the chief of the Child Neurology Division,
Department of Pediatrics
All India Institute of Medical Sciences, Delhi)opiNioN
ThE wEAPon hAS
To bE holISTIc
Recurring AES outbreaks demand preventive measures
Dr ShEFFAlI such as vaccinations and better preparedness on the ground
GulATIEarly identification
and immediate
treatment may be the
most crucial steps in
cases of AES.PTi8 July 2019 OutlOOk 41