Chapter 16: Episodes in Neonates, Infants, and Toddlers Mimicking Epilepsy

OVERVIEW

The misdiagnosis of epilepsy is common in infancy and childhood,^1,2,3,4 This book is devoted to epilepsy treatment, but if therapy is given for epilepsy that does not exist, then the result may be deleterious to the patient. This chapter outlines the conditions in neonates, infants, and toddlers that may beguile the physician (and even the surgeon) into misdiagnosis.

DEFINITIONS OF EPILEPSY

Past the neonatal period, the definition of an epileptic seizure is fairly straightforward, with the presumption that were an EEG recorded in a seizure, paroxysmal ictal discharges would be evident. Epilepsy is defined as repeated unprovoked epileptic seizures. However, in neonates and very young infants the epileptic "discharge" may appear as a suppression or attenuation of the EEG⁵ and the epileptic discharge must be inferred by the observer.

TIME LINE OF PAROXYSMAL PHENOMENA EMERGENCE

For this chapter, the disorders or phenomena are arranged according to median age of first appearance to the parent or the doctor. With notable exceptions,^6,7,8,9 median age of onset (MA) is seldom specified in the literature. Episodic events that are liable to be misdiagnosed as epilepsy with a MA of up to age 2 years will be reviewed.

HYPEREKPLEXIA (MA DAY 1)

The MA of 1 day does not take into account the onset of symptoms in fetal life (aside from hyperekplexia, "convulsive" fetal movements are best known in pyridoxine dependency but are also seen in cerebral malformations, and other rarer causes of epilepsy). Those with dominantly inherited hyperekplexia due to a mutation in a glycine receptor subunit, especially GLRA1, are stiff infants or neonates, and while they may be at risk of apnea and sudden death they are not usually misdiagnosed as having epilepsy. However, in "sporadic" cases^{10,11,12,13,14,15,16,17} and in those with mutations in the glycine transporter gene¹⁸ prominent nonepileptic neonatal seizures are an important feature.

Vigevano et al¹⁰ and Bernardina et al¹¹ gave the first detailed clinical descriptions of the nonepileptic seizures in neonatal hyperekplexia. Aside from massive myoclonic jerks, symptoms were marked by diffuse muscle stiffness, extension of all limbs, and intense cyanosis with bradycardia. The attacks were resistant to intravenous diazepam and oral phenobarbitone, nitrazepam and clonazepam.¹⁰ Spontaneous and induced generalized attacks with "sudden massive stiffness and shaking of the limbs lasting one to several minutes, and the mimicked generalized clonic or myoclonic fits" might induce severe bradycardia necessitating cardiac massage.¹¹ A published polygraphic recording¹¹ of one of these attacks that was tonic and vibratory revealed high-voltage repetitive muscle potentials in the upper and lower limb muscles, on most of the EEG channels and on the ECG channel. ...