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of LGI‑1‑LE [62] and in all the patients reported, led prevent the onset of LE. The FBDS was first described
[10]
to pacemaker implantation. Interestingly, in other in 2008 by Irani et al. and then better characterized in
cell‑surface antibody‑associated neurological 2011. As compared to the initial descriptions, it is now
[11]
disorders (i.e. N‑methyl‑D‑aspartate receptor antibody evident that the age of onset of FBDS is broad, varying
encephalitis) bradycardia has been rarely reported. from 28 to 92 years, [65,66] possibly with a small male
prevalence. [11,65] The daily frequency of FBDS is high,
FBDS represent a typical manifestation that may ranging from 6 to 360 attacks per day at their peak.
[11]
precede the development of LGI‑1 LE. The clinical Emotions and movements are common triggers of
[11]
features of FBDS will be extensively discussed FBDS, [11,65] and a sensory aura or auditory hallucinations
elsewhere in this review. They may be characterized may precede them. Every FBDS is characterized by
[65]
by facial twitching, hand and leg posturing. The a dystonic posturing of the arm, both proximally and
antiepileptic drugs do not usually reduce seizure distally, and may involve also the ipsilateral face and
activity. In contrast, early initiation of plasma less commonly, the trunk and the ipsilateral leg. It is
exchange and immunosuppression help to avoid the worth noting that events involving the leg alone have
development of full‑blown LE. been rarely observed. Furthermore, synchronous
[65]
bilateral dystonia and rapidly alternating events have
Routine cerebrospinal fluid (CSF) analysis may been reported. Either side can be involved, but FBDS
[65]
reveal a mild lymphocytosis in some patients and are usually unilateral on any occasion. [11] If FBDS can be
protein, and glucose levels may be modestly raised or classified as tonic seizures, or as a movement disorder,
within normal limits. Polymerase chain reaction is namely a form of dystonia, is still a matter of debate
[67]
obviously negative for herpes simplex virus and other and data to support the former and the latter hypothesis
neurotropic viruses while oligoclonal bands may be are summarized in Table 1. FBDS are often accompanied
present, but rarely unmatched with serum bands. [9] by ictal automatisms and may be, followed by fear,
agitation and speech arrest. The duration of FBDS was
[65]
In a recent magnetic resonance imaging (MRI) reported to last < 3 s in the early description, however
[11]
study on patients affected by VGKC‑LE [59] initial it is now clear that they may last also between 10 and
MRI findings included unilateral or bilateral 30 s. Serum sodium levels are often reduced in FBDS
[65]
amygdala and/or hippocampal enlargement and T2 patients presenting also with cognitive impairment but
hyperintensity in 78.6% of patients at some time point are rarely low during the period with facio‑brachial
during the disease course. Restricted diffusion, mild dystonic seizures alone. [11,65] If the patient experiences
ill‑defined contrast enhancement, and extratemporal FBDS alone, with no cognitive impairment, routine
findings were also reported. Interestingly, more than MRI is unremarkable in the vast majority of cases. [11,65]
a quarter of the patients with initially negative MRI However, routine MRI showed a high signal change
or only unilateral abnormalities then progressed to in the putamen in a patient described by Irani et al.
[65]
bilateral involvement, supporting the hypothesis of
radiologic progression of the disease. It is still a matter Table 1: Data to support the hypothesis of FBDS as tonic
of debate whether these changes reflect persistent seizures, or as a movement disorder
inflammation or alternatively they are secondary to Movement disorders Epileptic seizures
Loss of consciousness not The majority of patients experiences
recurrent seizures. In fact, patients with VGKC‑LE always noted loss of awareness, although not
have a very high frequency of epileptic seizures, [58] during every attack
and this has been hypothesized to be related to the Electroencephalography: Electroencephalography: focal
development of mesial temporal sclerosis, often epileptic activity in a slowing or epileptiform changes
minority of patients (24%) in 24% of cases with FBDS is a
seen in follow‑up VGKC‑LE patients. Patients with significant proportion (very brief
VGKC‑LE and high signal in the medial temporal duration of the attacks arising from
lobes typically develop hippocampal atrophy as the spatially limited or deep foci)
high signal declines. [63,64] It is not clear yet whether Functional Brief duration and highly stereotyped
attacks
neuroimaging: altered
the cases of otherwise “cryptogenic” mesial temporal glucose metabolism in
sclerosis are at least partly related to a remote effect of different cerebral regions,
VGKC autoimmunity. including basal ganglia
Poor response to LGI‑1 antibodies associated with
antiepileptic drugs typical medial temporal lobe seizures
FBDS in the context of limbic encephalitis,
FBDS are very brief highly distinctive seizures often refractory to anticonvulsants
associated with VGKC‑complex antibodies, almost Chorea and other The frequent ictal presence of
always in the LGI‑1 subtype. They carry a high chance movement disorders automatisms, and fear, agitation and
associated with VGKC
speech arrest after the motor event
of developing VGKC‑LE, and their recognition should FBDS: facio‑brachial dystonic seizures; VGKC: voltage‑gated potassium channels;
prompt consideration of immunotherapies in order to LGI‑1: leucine‑rich, glioma inactivated 1

72 Neuroimmunol Neuroinflammation | Volume 3 | March 28, 2016