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Nocturnal Frontal Lobe Epilepsy – An Update on Differential Diagnosis
a single night of recording, the Australian group tried to establish the deambulatory behaviours (known as epileptic nocturnal wanderings). They
reliability of anamnestic characteristics to distinguish NFLE from NREM may involve large neuronal networks, sometimes with emergence from the
when video-PSG is unavailable or unhelpful. On the basis of previous frontal zone (orbitofrontal, anterior cingulated), but also with spreading to
analyses and of practical experience, they developed a scale – Frontal temporal limbic cortices.
13,14
Moreover, some motor behaviours in this type
Lobe Epilepsy and Parasomnias (FLEP) – with questions and possible of attack are not very different from some confusional arousals or
answers determining a score. Responses favouring epilepsy score sleepwalking episodes typical of NREM arousal parasomnias. The concept
positively and those favouring parasomnias score negatively. These of the disinhibition of the innate motor pattern by central pattern
particular questions have been developed in a pilot subgroup of patients generators may explain these similarities, as well as the possible co-
with a definite diagnosis, who were excluded from the application study. existence in the clinical history (or in the familial tree) of parasomnia
episodes in people affected by NFLE or seizures during sleep.
3,6,8
The guidelines for differentiating epileptic from non-epileptic motor
…there may be a continuum between
phenomena during sleep provided by the Italian group article originated in
some observed and verified statements. These were that behaviour
physiological movements in sleep,
patterns may be similar, semiological characteristics are not present in all
motor behaviour in parasomnia and
the episodes – bearing in mind that the description by a witness may be not
complete and adequate – and, finally, that clinically diagnostic tools –
some epileptic seizures.
including EEG, video-PSG and video recording at home – are unreliable.
The authors reviewed the clinical aspects and features of the major
motor phenomena during sleep and elaborated on remaining issues.
They compared the clinical diagnosis by FLEP scale with standard They concluded that video-PSG analysis is of the utmost importance,
diagnostic tests – video-PSG and expert interviews – in a group of but, due to lack of ictal and interictal scalp EEG abnormalities, is
patients coming under observation for nocturnal episodes of uncertain sometimes difficult to interpret. Furthermore, a debate is still open on
definition. Three groups were defined – NFLE (31 patients), typical the aetiopathogenesis of different epileptic and non-epileptic motor
parasomnias (20 patients) and atypical parasomnias (11 patients). phenomena during sleep.
2–4
The genetic form of NFLE – autosomal-
dominant NFLE (ADNFLE) – has been linked to different mutations in
The FLEP scale consists of 11 questions covering characteristics of the the gene coding for neuronal nicotinic acetylcholine receptors
nocturnal attacks including age at onset, duration, clustering and timing (nAChR), but the exact mechanisms by which these mutations may
of the episodes, symptoms, stereotypy, recall and vocalisation. According modify the firing of neurons giving origin to seizures is not completely
to the results, only three patients were erroneously classified by the understood.
15
Moreover, arousal disorders are often aggregated on a
non-medically trained, and two by the medically trained interviewer. In all family basis and, in patients with NFLE, sporadic or genetic, we found
cases, patients with atypical parasomnias with a low positive score were co-existence of nocturnal parasomnic episodes or the presence of
classified as having NFLE. The scale reached a sensitivity of 1 and a these attacks in family members.
2–6
specificity of 0.9, with a Cohen k of 0.97 between different interviewers;
notwithstanding the retrospective type of the study and the lack of video-
PSG confirmation of typical parasomnias, the scale seems promising for
the differential diagnosis of NFLE and parasomnias. However, the results
…debate is still open on the
need to be confirmed in a larger group of subjects and controlled in all
the subjects with video-PSG.
10
aetiopathogenesis of different
epileptic and non-epileptic motor
However, the weakness of the study is that the clinical features of the
phenomena during sleep.
episodes are often neither completely nor well described by the bed
partner, and the features of the attacks (stereotypy, repetitiveness,
wandering or other characteristics) may belong both to parasomnias and
seizures. This, in accordance with the theory that motor events may
follow a stereotyped inborn fixed action pattern (motor central pattern Considering the central motor pattern generator theory, it is also possible
generators), means that the syndrome is genetically determined and that the genetic or sporadic alteration lies in the mechanisms controlling
triggered by a common platform – the arousal network.
11
Thus, there the arousal system, which explains why sometimes, or in some subjects,
may be a continuum between physiological movements in sleep, motor we can expect arousal disorders or epileptic seizures by the same
behaviour in parasomnia and some epileptic seizures. These activation but with different triggers – epileptic abnormalities or
considerations make clinical diagnosis intriguing but also difficult, and sleep-related dysfunctions.
11,16
In support of this hypothesis, the authors
some concepts we have followed in the past years may not be completely collected data on familial aggregation of diagnosed NFLE patients and
applicable in this field.
5,8,12
found, in comparison with a control population, a higher frequency of
arousal parasomnias in NFLE probands and their relatives.
6
Sometimes, sleep-related seizures similar to those observed in NFLE may
arise from the temporal lobe rather than from orbitofrontal zones, in Furthermore, the intracerebral recording techniques have not
particular those characterised by affective symptoms and agitated and elucidated the problem. They helped to confirm the increasing
EUROPEAN NEUROLOGICAL DISEASE 2007 63
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