Juliana Ávila Duarte

The molar tooth sign and the bat wing appearance in Joubert syndrome

A 10-year-old female patient was brought to the outpatient clinic with a history of neurodevelopmental delay, gait and limb incoordination, and oculomotor apraxia. According to her parents, the girl had always showed delayed acquisition of motor milestones when compared to other children, which became more evident when she was 8 months old and was not able to sit. She was able to sit by age of 2, and walked independently, but unsteady, when she was 3.5 years old. She presented with cognitive impairment. Reviewing her history, it became clear that she was hypotonic at birth and subsequently developed gait ataxia in early childhood. She was born to nonconsanguineous parents and there were no other similar cases in her family. On physical examination, she held her head preferentially in a lateralized position to her right side. She showed gait ataxia in tandem walking, abnormal stance with a positive Romberg’s sign, dysmetria, dysdiadochokinesia, diffuse hyperreflexia, bilateral Babinski sign, and oculomotor apraxia. The Wechsler Intelligence Scale for Children-III (WISC-III) demonstrated an IQ of 67 (intellectual disability). There were no other abnormalities on physical examination. Electroencephalogram showed focal paroxysmal discharges of moderate intensity in the posterior parietal-temporal region. Brain magnetic resonance imaging (MRI) demonstrated agenesis of the cerebellar vermis with a slit in the medial line sparing the two cerebellar hemispheres (Figure 1), lengthening and thickening of the cerebellar peduncles, associated with reduction of the anteroposterior diameter of the mesencephalon, the so-called “molar tooth sign” (MTS) (Figure 2). Morphological alterations in the posterior fossa showed a 4th ventricle with a typical “bat wing” appearance (Figure 3). These findings were highly suggestive of Joubert syndrome (JS).

NTRK2 (TrkB gene) variants and temporal lobe epilepsy: A genetic association study

OBJECTIVEnThe NTRK2 gene encodes a member of the neurotrophic tyrosine kinase receptor family known as TrkB. It is a membrane-associated receptor with signaling and cellular differentiation properties that has been involved in neuropsychiatric disorders, including epilepsy. We report here the frequencies of NTRK2 allele variants in patients with temporal lobe epilepsy (TLE) compared to controls without epilepsy and explore the impact of these polymorphisms on major clinical variables in TLE.nnnMETHODSnA case-control study comparing the frequencies of the NTRK2 gene polymorphisms beween 198 TLE Caucasian patients and 200 matching controls without epilepsy. In a second step, the impact of allelic variation on major clinical and electroencephalographic epilepsy variables was evaluated in the group of TLE patients. The following polymorphisms were determined by testing different regions of the NTRK2 gene: rs1867283, rs10868235, rs1147198, rs11140800, rs1187286, rs2289656, rs1624327, rs1443445, rs3780645, and rs2378672. To correct for multiple correlations the level of significance was set at p<0.01.nnnRESULTSnPatients with TLE showed a statistical trend for increase of the T/T genotype in rs10868235 compared to control (O.R.=1.90; 95%CI=1.17-3.09; p=0.01). Homozygous patients for the A allele in rs1443445 had earlier mean age at onset of seizures, p=0.009 (mean age of 16.6 versus 22.4years). We also observed that the T allele in rs3780645 was more frequent in patients who needed polytheraphy for seizure control than in patients on monotherapy, (O.R.=4.13; 95%CI=1.68-10.29; p=0.001). This finding may reflect an increased difficulty to obtain seizure control in this group of patients. No additional differences were observed in this study.nnnCONCLUSIONSnPatients with epilepsy showed a trend for a difference in rs10868235 allelic distribution compared to controls without epilepsy. NTRK2 variability influenced age at seizure onset and the pharmacological response to seizure control. As far as we know, this is the first study showing an association between NTKR2 allelic variants in human epilepsy. We believe that further studies in this venue will shade some light on the molecular mechanisms involved in epileptogenesis and in the clinical characteristics of epilepsy.