Dr.Sheila Mathai, MD,DNB,DM*
Associate Professor Department of Pediatrics
Armed Forces Medical College, Pune-411040*
|The term neonate with features of altered sensorium and seizures is an emergency. "Neonatal encephalopathy" has emerged as the preferred terminology to describe this state of central nervous system dysfunction, as it does not imply a specific underlying pathophysiology. Birth asphyxia and hypoxic-ischemic encephalopathy was once considered responsible for nearly all such cases, but it is now recognized that neonatal encephalopathy can result from a wide variety of conditions and often remains unexplained. Similarly, the underlying nature of brain injury causing neurologic impairment in a newborn is often poorly understood. There is as yet no consensus definition of neonatal encephalopathy. Some investigators require stringent criteria, such as two or more symptoms of encephalopathy, lasting over 24 hours. Though in most cases the diagnosis may be obvious (as in asphyxia), in a number cases this can be a diagnostic challenge. This is especially with inborn errors of metabolism in which early diagnosis and management may prevent morbidity and give an opportunity for treatment and genetic counseling.
Encephalopathies in the neonate can be broadly classified as asphyxial, infective, metabolic or vascular. Hypoxic Ischaemic Encephalopathy or HIE is characterized by the typical history and progression along with multisystem organ involvement and should form part of the ACOG Criteria for perinatal hypoxic- ischaemic injury, Vascular encephalopathies may be catastrophic or insidious. These may be due bleeds, infarcts or thrombosis in a neonate with or without risk factors like polycythemia or thrombogenic states. Infective encephalopathy is usually part of sepsis and has a multifactorial etiology. It should be noted that some Inborn Errors of Metabolism (IEMs) also make the neonate more susceptible to sepsis. IEMs are not as rare as we assume them to be and should be considered in the differential diagnosis.
Approach to a neonate with encephalopathy should be broad-based to start with and then follow a logical sequence to arrive at a definitive diagnosis as soon as possible. In many cases, this is a diagnosis of exclusion. Clinical clues including a sound history often pay rich dividends. A strong family history of early neonatal deaths should arouse obvious suspicion. The single most important indicator of an IEM is an altered neurological status disproportionate to systemic symptoms and signs. Asphyxia sufficient to produce altered neurological status is often accompanied by acute rental tubular necrosis or other systemic involvement. Sepsis causing encephalopathy is usually accompanied by meningitis and shock. Among the IEMs severe encephalopathy is seen typically with aminoacidopathies, organic acidemias and fatty acid oxidation defects.
Investigations should include tests to look for disproportionate acidosis (pH < 7.0) hyperammonia levels > 1000 mmol/L and neuroimaging. An EEG is good for prognostication as a normal background is associated with normal outcome in > 90% of cases.
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