Cerebellum-dependent associative learning is not impaired in a mouse model of neurofibromatosis type 1

Individuals with Neurofibromatosis type 1 (NF1) experience a high degree of motor problems. The cerebellum plays a pivotal role in motor functioning and the NF1 gene is highly expressed in cerebellar Purkinje cells. However, it is not well understood to what extent NF1 affects cerebellar functioning and how this relates to NF1 motor functioning. Therefore, we subjected global Nf1^+/- mice to a cerebellum-dependent associative learning task, called Pavlovian eyeblink conditioning. Additionally, we assessed general motor function and muscle strength in Nf1^+/- mice. To our surprise, we found that Nf1^+/- mice showed a moderately increased learning rate of conditioned eyeblink responses, as well as improved accuracy in the adaptive timing of the eyeblink responses. Locomotion, balance, general motor function, and muscle strength were not affected in Nf1^+/- mice. Together, our results support the view that cerebellar function in Nf1^+/- mice is unimpaired.

Motor cortical excitability and plasticity in patients with neurofibromatosis type 1

OBJECTIVE

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder that is associated with cognitive disabilities. Based on studies involving animals, the hypothesized cause of these disabilities results from increased activity of inhibitory interneurons that decreases synaptic plasticity. We obtained transcranial magnetic stimulation (TMS)-based measures of cortical inhibition, excitability and plasticity in individuals with NF1.

METHODS

We included 32 NF1 adults and 32 neurotypical controls. Cortical inhibition was measured with short-interval intracortical inhibition (SICI) and cortical silent period (CSP). Excitability and plasticity were studied with intermittent theta burst stimulation (iTBS).

RESULTS

The SICI and CSP response did not differ between NF1 adults and controls. The response upon iTBS induction was significantly increased in controls (70%) and in NF1 adults (83%). This potentiation lasted longer in controls than in individuals with NF1. Overall, the TMS response was significantly lower in NF1 patients (F(1, 41) = 7.552, p = 0.009).

CONCLUSIONS

Individuals with NF1 may have reduced excitability and plasticity, as indicated by their lower TMS response and attenuation of the initial potentiated response upon iTBS induction. However, our findings did not provide evidence for increased inhibition in NF1 patients.

SIGNIFICANCE

These findings have potential utility as neurophysiological outcome measures for intervention studies to treat cognitive deficits associated with NF1.

Discomfort and pain in newborns with myelomeningocele: a prospective evaluation

OBJECTIVE

In a worldwide debate on deliberately terminating the lives of newborns, proponents point at newborns with very severe forms of myelomeningocele (MMC) and their assumed suffering, claiming there are no effective means of alleviating their distress. Nevertheless, the degree of discomfort and pain in these newborns has never been assessed in a structured manner.

METHODS

In a prospective cohort study, 28 consecutive newborns with MMC were included over a 5-year period and were followed up throughout their hospital stay for initial treatment. We created 2 disease severity groups on the basis of the Lorber criteria. The primary outcomes were discomfort and pain, assessed by simultaneously scoring 2 validated scales: the visual analog scale for pain and the Comfort Behavioral Scale for discomfort. These scores were coupled to a validated and evidence-based analgesia algorithm.

RESULTS

Overall, discomfort related to pain was measured in 3.3% of the scores. This percentage differed little between the preoperative and postoperative periods and did not significantly differ between newborns with less severe MMC and severe MMC (3.9% vs 2.8%; P = .3). The mean dosage of paracetamol was 35 mg/kg per day (95% confidence interval: 32-39); the mean dosage of morphine was 0.9 μg/kg per hour (95% confidence interval: 0.6 -1.2).

CONCLUSION

Over the length of their hospital stays for initial treatment, all newborns with MMC presented with low levels of discomfort and pain independent of disease severity and time frame.