Non Epileptic Motor Attacks Mimicking Clonic Seizures in Children

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Seizure 21 (2012) 147–150

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Case report

Extremely sustained startle-induced clonus: Non epileptic motor attacks

mimicking clonic seizures in children with encephalopathy

a a a a,b,

Francesco Mari , Simone Gana , Francesca Piras , Renzo Guerrini *

Paediatric Neurology Unit and Laboratories, Paediatric Hospital A. Meyer – University of Florence, Florence, Italy

IRCCS Fondazione Stella Maris, Calambrone, Pisa, Italy

A R T I C L E I N F O A B S T R A C T

Article history: Clonus is a pathological motor pattern characterised by involuntary, rhythmic and brisk muscular

Received 29 June 2011

contractions in response to peripheral stimuli producing muscle stretching. It indicates pathological

Received in revised form 26 September 2011

involvement of the corticospinal tract and can be considered as a functional spastic movement disorder of

Accepted 27 September 2011

variable clinical presentation and duration. We documented severe and prolonged episodes of startle-

induced clonic attacks associated with severe apnoea, occurring in three infants with severe

Keywords:

encephalopathy. The clinical characteristics of such episodes are very similar to those of clonic epileptic

Clonus

seizures. Video-EEG recordings conﬁrmed the non epileptic origin of the episodes. Previous anti-epileptic

Startle-induced seizures

drug treatment was unsuccessful but myorelaxing drugs produced a dramatic improvement.

Clonic seizures

1. Introduction distress appeared, requiring intubation and ventilatory assistance.

During his second day of life, frequent and prolonged paroxysmal

Clonus is deﬁned as a functional spastic movement disorder events characterised by startle-induced stiffness with apnoea

that indicates pathological involvement of the corticospinal tract. appeared. Brain MRI, performed on the 5th day of life, revealed

It is characterised by involuntary, rhythmic (5–8 Hz) and brisk bilateral hyperintensity of basal ganglia, which was consistent

muscular contractions in response to peripheral stimuli producing with early asphyxia. Interictal electroencephalogram (EEG)

muscle stretching. Clonus is usually seen after stroke, in multiple showed multifocal paroxysmal activity. A tentative diagnosis of

sclerosis, as a consequence of brain and spinal cord injuries and startle-induced epilepsy was made and treatment with midazolam

other CNS lesions leading to pyramidal system impairment. Its and phenobarbital was introduced, without beneﬁt. In early

spatial and temporal distribution are variable as it may involve just infancy, multiple per day, prolonged episodes of startle persisted,

a restricted somatic area or be diffuse and persist for just a few progressing into rhythmic clonic jerks, with stiffness and apnoea.

seconds to minutes. We documented prolonged episodes of Antiepileptic drugs produced no beneﬁt. At the age of 7 months,

startle-induced clonic attacks spreading to the whole body and the child was referred to our Unit. On physical examination,

producing apnoea, in three infants with severe encephalopathy. microcephaly with severe global developmental delay, and spastic-

The clinical characteristics of such episodes are clinically hypokinetic quadriplegia were apparent. Numerous clonic ﬁts with

indistinguishable from those of startle-induced clonic epileptic relevant apnoea were video-EEG recorded (see Video, Segment 1),

seizures with which they had been misdiagnosed before their non which occurred with no concomitant EEG change (see Fig. 1A).

epileptic pathophysiology was clariﬁed. Holding the patient’s jerking limbs down reduced the duration of

the attacks. Antiepileptic drug therapy was discontinued and

myorelaxing treatment with clonazepam and oral baclofen was

2. Case reports

started with dramatic improvement. Laboratory examinations

(including routine blood and urine tests, and screening tests for

Patient 1 is a 2 years old Chinese boy, who was born at term and

metabolic defects) were normal. Mutation analysis of the alpha1

with unremarkable family history. Head circumference at birth

subunit of inhibitory glycine receptor gene (GLRA1) resulted

was normal. In the immediate postnatal period, respiratory

negative. Brain MRI revealed severe diffuse cortical and subcortical

atrophy sparing the brainstem and cerebellum (see Fig. 2A 1-2).

Patient 2 is a 2 years old boy, who was born at term and with an

* Corresponding author at: Paediatric Neurology Unit and Laboratories,

unremarkable family history. Birth weight, height and head

Children’s Hospital A. Meyer – University of Florence, Viale Pieraccini 24, 50139

circumference were appropriate for gestational age. At 1 month

Firenze, Italy. Tel.: +39 0555662573; fax: +39 0555662329.

E-mail address: [email protected] (R. Guerrini). of age, the patient was hospitalised for investigation of severe

148 F. Mari et al. / Seizure 21 (2012) 147–150

Fig. 1. Ictal poligraphic recordings in Patients 1 and 2 (A and B, respectively): at (*), acoustic (A) and proprioceptive (B) stimuli were delivered causing startle-responses

followed by rhythmic EMG bursts with no concomitant EEG changes.

developmental delay and frequent episodes of sustained jerking. bilateral cataract. Brain MRI revealed cerebellar vermis hypoplasia

Neurological examination revealed severe axial hypotonia, poor and bilateral hyperintensity of basal ganglia. He was discharged

sucking, dysphagia (that later required the placing of percutaneous with a diagnosis of startle-induced seizures and encephalopathy of

endoscopic gastrostomy, PEG), extremely brisk reﬂexes, and unknown etiology, and antiepileptic treatment with phenobarbital

frequent, spontaneous or startle-induced, episodes of whole body and carbamazepine. No relevant effects on the frequency of the

stiffness and clonic jerking. Screening tests for metabolic defects clinical episodes were noticed.

resulted normal. EEG showed slow background activity and At the age of 12 months, the child was referred to our Unit.

multifocal abnormalities. Ophthalmologic assessment evidenced Neurological examination revealed severe developmental delay,

F. Mari et al. / Seizure 21 (2012) 147–150 149

Fig. 2. Coronal and axial T2 sequences on MR examination revealing severe diffuse brain atrophy in Patient 1 (A, 1-2), Patient 2 (B, 1-2) and Patient 3 (C, 1-2).

spastic-hypokinetic quadriplegia and microcephaly. Frequent epi- intensity of attacks. A second brain MRI revealed severe diffuse

sodes of low-threshold startle reaction, followed by stiffness, cortical and sub-cortical atrophy (see Fig. 2B 1-2).

clonic jerks and apnoea were video-EEG recorded (see Video, Patient 3 is a 18 months old girl whose clinical history is only

Segment 2 and Fig. 1B). Myorelaxing treatment with oral baclofen partially known. She was born at term after an apparently

was introduced with remarkable reduction in the frequency and uncomplicated pregnancy. However, severe developmental delay

150 F. Mari et al. / Seizure 21 (2012) 147–150

was noticed since her ﬁrst months of life. Severe spastic- tract. A large number of CNS lesions or disorders involving the

hypokinetic quadriplegia became apparent and brain MRI scan pyramidal system are known to be causative. The clinical pattern

revealed massive cortical and subcortical atrophy, which was of clonus observed in our patients was remarkable for its long

attributed to prenatal suffering (see Fig. 2C 1-2). Prolonged duration and somatic spreading, leading to severe apnoea, and was

episodes of twitching and rhythmic clonic jerking appeared probably related to the massive cortical and subcortical atrophy.

during the ﬁrst months of life and were initially interpreted as Although clonus’ underlying mechanisms are not yet complete-

clonic epileptic seizures. However, clinical observation and ly understood, an interaction between central mechanisms and

10,11

video-EEG recordings were consistent with startle-induced peripheral events has been proposed with, as main mecha-

stiffness and clonic twitching of non epileptic origin. In nism, a strong facilitation of descending motor pathways from the

particular, we noticed that the episodes of jerking were brain to the spine.

regularly precipitated by tapping and stretching and were In all three patients, the speciﬁc cause of the extremely severe

terminated by interrupting the reverberating spinal reﬂex by brain atrophy remained unclear. It is possible that the extremely

holding the patient’s jerking limbs down (see Video, Segment 3). frequent and prolonged apnoic episodes have contributed in

The patient was lost from follow-up and no information on causing chronic post-anoxic damage superimposed to the origin-

treatment was available. ary perinatal brain lesion.

In all three cases, a written informed consent for publication of Our opinion is that the clinical manifestation we have described

the videos has been obtained. is probably under-diagnosed and easily misdiagnosed as epileptic

seizures. This report shows that careful video-EEG recordings are

3. Discussion required for a proper differential diagnosis of paroxysmal motor

phenomena, particularly in children with severe brain damage

Our reports disclose the fundamental role of a careful who are at risk of exhibiting complex neurological disorders.

neurophysiological evaluation for the differential diagnosis of Recognition of a non epileptic phenomenon in our patients

3,4

paroxysmal motor phenomena in severely disabled infants. permitted to avoid useless AEDs therapies and to introduce

Using video-EEG monitoring we captured many episodes of clonic myorelaxing drugs with remarkable clinical beneﬁt.

ﬁts with relevant apnoea and delineated their peculiar electro-

clinical characteristics. These were inconsistent with the previous

Conﬂict of interest

diagnosis of startle-reﬂex seizures and rather suggested an

extremely sustained form of clonus, spreading to the whole body.

None declared.

Polygraphic ﬁndings were not consistent with the classical

picture of clonic seizure ; no ictal discharges or post-ictal inactive

Acknowledgement

and ﬂat tracings were seen and the accompanying EMG bursts

were of relatively low and constant frequency (between 4 and

This research was not externally funded.

7 Hz), neither reaching the average rates observed in clonic

seizures (about 10 Hz) nor modifying their frequency and intensity

(see Fig. 1).

Appendix A. Supplementary data

Besides, a careful review of the clinical histories of our patients

highlighted the absence of some characteristics of ‘‘Startle

epilepsy’’. In this severe symptomatic epileptic syndrome, Supplementary data associated with this article can be found, in

startle-reﬂex epileptic episodes typically exhibit the character- the online version, at doi:10.1016/j.seizure.2011.09.011.

istics of tonic seizures and, less commonly, of other ictal patterns

(such as clonic episodes). Moreover, the absence of spontaneous References

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