The developmental and epileptic encephalopathies (DEEs) are the most severe group of epilepsies in which frequent epileptic activity, in addition to the underlying etiology, contributes to developmental impairment, with onset typically in infancy or childhood (1). At least 50% of the DEEs have a genetic cause (2), and there is significant etiological overlap with other neurodevelopmental disorders such as intellectual disability (ID) and autism spectrum disorder (3).

The Neurite EXtension and MIgration Factor gene (NEXMIF), previously called KIAA2022 (OMIM 300524), is an X-linked gene thought to play an important role in early brain development (4–7). Pathogenic NEXMIF variants were first identified in males with non-syndromic X-linked ID with poor or absent speech, subtle dysmorphic features, and sometimes epilepsy (8, 9). Subsequently, affected females have been described (10–14) and recently a large multicentric study outlined the epilepsy phenotype of affected females (15) which is consistent with a generalized DEE characterized by myoclonic–atonic epilepsy overlapping with eyelid myoclonia with absence. Notably a considerable proportion of affected females present prolonged seizures characterized by absence status with eyelid myoclonia (15, 16). We report a female patient with a de novo NEXMIF pathogenic variant and recurrent prolonged episodes of absence status with eyelid myoclonia. In order to evaluate the consequences of NEXMIF mutation at brain structural and functional MRI level (17) two different studies were carried out comparing the patient with respect to patients with genetic generalized epilepsy (GGE; formerly idiopathic) and healthy controls (HC).

The patient is a 28-year-old woman, with a drug-resistant epilepsy starting at the age of 9 years with recurrent episodes of prolonged non-convulsive status epilepticus (NCSE) characterized by mydriasis, eyelid myoclonia and reduced responsiveness to environmental stimuli with a frequency of 1–2 episodes/month. She was born pre-term (8th gestational month) from a dichorionic diamniotic twin pregnancy, from unrelated parents. Family history is unremarkable for epilepsy, febrile seizures, and any other neurological condition. Her developmental milestones were slightly delayed (she started walking at 16 months and talking at 24 months). She afterwards achieved borderline intellectual functioning (full-scale IQ 75 at the age of 24 years; WAIS) with difficulties in visuo-spatial information processing and dyspraxia. The patient also presented night terrors and enuresis until late adolescence. Her neurological examination is unremarkable.

During NCSE, which may last up to 48 h, the patient first complains of an epigastric discomfort, followed by headache and subsequent clouding of consciousness when she becomes progressively more unaware and detached from the environment. During this phase, the patient has mydriasis and presents subcontinuous eye-blinking. EEGs recorded during NCSE show a continuous, diffuse, spike- and poly-spike and wave-discharge, worsened by eye closure, hyperventilation and by intermittent photic stimulation (Supplementary Figure 1). Characteristically eye closure induces the paroxysmal discharges while these tend to reduce or disappear when the patient is asked to open her eyes/stare or to perform a mental task. Beyond these episodes the patient's EEG background activity appears normal, with only occasional diffuse sharp waves, mainly elicited by eye closure.

Various anti-seizure medications (ASM) in numerous combinations were tried without achieving substantial benefit. She was first started on valproic acid, with clonazepam, and then switched to topiramate because of lack of efficacy. Lamotrigine, lacosamide, zonisamide, acetazolamide and ethosuximide were ineffective or even detrimental. A vagal nerve stimulator was implanted at the age of 25 years. At the time of this report, the patient is on valproate (1,000 mg), lamotrigine (150 mg) and brivaracetam (150 mg) but continues to have recurrent NCSE even if more rarely than in the past.

Extensive metabolic and endocrinological screening showed no significant abnormalities except for secondary amenorrhea. Liver and renal functions are normal, and no alterations were found on abdominal ultrasound and echocardiography. Brain structural MRI shows no abnormality.

NEXMIF plays an important role in neural circuit formation during development (4–8). Knockdown of NEXMIF leads to dramatic impairment in neurite outgrowth, with a particular impact on the lengths of dendrites and axons (9). To our knowledge, this is the first study to attempt to identify whether pathogenic NEXMIF variants induce alterations in brain structure or in functional networks in humans. In summary, compared to other populations, the studied patient shows a thinning of the prefrontal cortex and in particular of the middle frontal gyrus, of the temporal lobe cortex (including the fusiform gyrus) and of pericalcarine visual cortex. Consistently, these areas have shown functional alterations (increase of BOLD signal compared to controls) in the condition of eye closure: this finding is of interest because this pattern of functional activation was previously documented in patients with a clinical phenotype characterized by eyelid myoclonia and absences (27). In fact, the patient, although not having the clinical phenotype typical of Jeavons syndrome, demonstrated prolonged NCSE episodes characterized by absences with eyelid myoclonia.

Here the use of advanced neuroimaging techniques in a specific genetic phenotype revealed brain structural and functional changes that can bring the clinical phenotype to alteration within specific brain networks, and especially in networks physiologically involved in several visuomotor function, including the motor control of eye-closure and eye-movements, and attention to visual targets. Notably, it is not possible to determine whether the observed morphometric alterations are ascribable to the dysfunction of the NEXMIF gene primarily, or what role has the repetition of prolonged NCSE on these regions. Indeed, this study needs replication in both males and females carrying pathogenic gene mutations in NEXMIF gene to come to the conclusion that the observed network alterations are gene specific, or mutation mediated effects, or a feature of the association of epileptic seizure phenotype of eyelid myoclonia with absences. To note, it is unlikely that the observed structural/functional MRI changes are result of single gene defect but may be the consequence of effects mediated by more than one gene involved in the development of visuomotor networks. Of course, the results obtained should be considered with caution and reflect patient-specific brain changes. That said, the study has identified consistent alterations in cortical/subcortical morphometry and functional imaging thus providing a link between the genetic alteration and in vivo brain functioning/morphology.

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found below: Dryad [https://doi.org/10.5061/dryad.kwh70rz49].

The studies involving human participants were reviewed and approved by Comitato Etico Provinciale, Azienda Ospedaliero-Universitaria di Modena (study no. 80/10 and 268/15). Written informed consent to participate in this study was provided by the participants' legal guardian/next of kin. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

MC, AC, AV, GG, and SM contributed to the conception of the subject of the manuscript. MC, AC, and SM searched the patient files, interpreted literature, and wrote the manuscript. AC, MI, FZ, SK, and SS contributed to the genetic analysis and genetic interpretation of data. MT, AV, and SM performed the fMRI data analysis. AC, GG, SS, and SM revised the manuscript.

This research was partly funded by a Grant on Genetic Epilepsies issued by Fondazione LICE to AC. SS is supported by the Epilepsy Society.

AC has received research grant support from the Ministry of Health (MOH) and has received personal compensation as scientific advisory board member for EISAI, BIAL, and GW pharmaceutical Company. SM received research grant support from the Ministry of Health (MOH); has received personal compensation as scientific advisory board member for UCB and EISAI. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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