Somatosensory system hyperexcitability in alternating hemiplegia
of childhood
C. Vollono
a
, S. Rinalduzzi
b
, R. Miliucci
c
, F. Vigevano
c
and M. Valeriani
c,d
a
Unit of Neurophysiopathology and Sleep Medicine, Department of Geriatrics, Neurosciences and Orthopedics, Catholic University, Rome;
b
Neurology Unit, ‘Sandro Pertini’ Hospital, Rome;
c
Neurology Division, Pediatric Hospital ‘Bambino Ges u’, IRCCS, Rome, Italy; and
d
Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark
Keywords:
alternating hemiplegia of
childhood, ATP1A3,
migraine, recovery cycle,
somatosensory evoked
potentials
Received 2 October 2013
Accepted 26 May 2014
Background and purpose: Alternating hemiplegia of childhood (AHC) is a rare neu-
rological disease characterized by recurrent paroxysmal attacks of hemiplegia. The
aim of the study was to assess the recovery cycle of the somatosensory evoked
potentials (SEPs) in a group of AHC patients.
Methods: Seven AHC patients and 10 control age-matched subjects (CS) were
recruited. Right and left median nerve SEPs were recorded. The somatosensory sys-
tem excitability was assessed by calculating the SEP changes after paired electrical
stimuli. All patients were studied during the interictal phase, whilst four patients
were studied also during the ictal phase.
Results: In AHC patients during the interictal phase, the amplitudes of the cervical
N13 and of the cortical N20, P24 and N30 responses showed a faster recovery than
in CS. In AHC patients during the ictal phase, the cortical N20 recovery cycle was
prolonged compared with the interictal phase.
Conclusions: A shortened SEP recovery cycle in AHC during the interictal phase
suggests multilevel somatosensory system hyperexcitability in AHC. A partial recov-
ery of this phenomenon during the ictal phase possibly reflects a functional reset of
the somatosensory system. Overall, there is a disinhibition of the somatosensory sys-
tem in AHC, a functional change of brain function associated with a possible
involvement of the Na
+
/K
+
channels. This abnormality and its partial recovery
during the attacks might be linked to the pathophysiological and genetic mecha-
nisms of the disease.
Introduction
Alternating hemiplegia of childhood (AHC) [1] is a
rare clinical syndrome that has hemiplegic attacks as
the major feature, at least in its initial clinical presen-
tation. AHC is characterized by (i) repeated episodes
of paralysis involving either side of the body; (ii)
attacks of quadriplegia starting either as generaliza-
tion of a hemiplegia episode or bilateral ab initio; (iii)
other paroxysmal phenomena, such as tonic/dystonic
spells, choreoathetotic movements, nystagmus, strabis-
mus, dyspnoea and autonomic phenomena, occurring
during hemiplegic attacks or isolated; (iv) immediate
cessation or consistent improvement of both weakness
and associated paroxysmal phenomena on falling
asleep, but with recurrence 10–20 min after awakening
in long-lasting attacks; (v) developmental delay, men-
tal retardation and permanent neurological abnormal-
ities. The disease is usually characterized by an onset
before 18 months of age [2]. The clinical course of
AHC is progressive and patients develop fixed neuro-
logical deficits such as choreoathetosis, dystonia,
ataxia and neurodevelopmental disturbances. Few
patients show signs of pyramidal tract involvement.
Epileptic seizures are reported in 19%–50% of
patients [3,4]. Neuroimaging studies are normal in a
variety of patients and autoptic examination has not
shown pathognomonic lesions of the brain [2,4–6]. A
study of regional cerebral blood flow showed relative
hyperperfusion of the contralateral cerebral hemi-
sphere during hemiplegic attacks versus normal and
symmetrical cerebral perfusion during the asymptom-
atic phase [7].
The disease is sporadic and recently two different
groups of researchers found several de novo mutations
Correspondence: C. Vollono, Unit of Neurophysiopathology and
Sleep Medicine, Department of Geriatrics, Neurosciences and
Orthopedics, Catholic University À Policlinico Agostino Gemelli,
Largo Agostino Gemelli 8, Rome, Italy (tel.: +39 0630154276;
fax: +39 0630151909; e-mail: lvol@libero.it).
© 2014 EAN
European Journal of Neurology 2014, 21: 1478–1485 doi:10.1111/ene.12516