Bands of Fontana are caused exclusively by the sinusoidal path of axons in peripheral nerves and predict axon path; evidence from rodent nerves and physical models

The precise cause of the bands of Fontana, striations on peripheral nerves visible to the naked eye, has been the subject of debate for hundreds of years. Some researchers have described them as reflecting the sinuous course of nerve fibres passing through nerves, and others have proposed that endoneurial collagen and sheaths surrounding nerves play a role in their appearance. We hypothesised that the bands are caused exclusively by reflection of light from the surfaces of nerve fibres travelling in phase in sinusoidal waveforms through peripheral nerves. We aligned images of obliquely illuminated nerves with confocal images of axons in those nerves, and the numbers and positions of the bands precisely matched the axonal waves. We also developed three‐dimensional models of nerves with representations of the sinusoidal path of axons at their surface. We observed patterns resembling the bands of Fontana when these models were obliquely illuminated. This provides evidence that the bands of Fontana can be caused by light reflected sinusoidal path of axons alone. We subsequently describe a mechanism of band production based on our observations of both nerves and models. We report that smaller diameter nerves such as phrenic nerves and distal branches of sciatic nerves have shorter band intervals than larger nerves, such as proximal trunks of sciatic nerves, and that shorter band intervals correlate with longer axons per unit length of nerve, which suggests a greater tolerance to stretch. Inspection of banding patterns on peripheral nerves may permit prediction of axon length within nerves, and assist in the interpretation of nerve conduction data, especially in diseases where axon path has become altered.     

Quality of life after hemifacial spasm surgery: French versions of the HFS-8 and HFS-30 questionnaires

ObjectivesThe aim of the present study was to assess quality of life before and after surgery for hemifacial spasm, in order to validate two specific quality of life scales translated in French. Surgical results and complications were reported.Material and methodsTwenty-three patients with hemifacial spasm treated by microvascular decompression were retrospectively included. The HFS-8 and HFS-30 quality of life scales were translated from English into French using a forward-backward method and implemented on patients at least one year after surgery.ResultsMedian HFS-8 and HFS-30 values were respectively 16 ± 12.5 (range: 8–20.5) and 38 ± 38.5 (range: 23–61.5) before surgery and 0.5 ± 4.5 (range: 0–4.5) and 5 ± 17.5 (range: 1–18.5) after surgery, showing significant improvement in quality of life (P < 0.001). The internal consistency of both scales was excellent (Cronbach's alpha > 0.9), and they were significantly correlated (Pearson coefficient = 0.95; 95% CI [0.91; 0.98]; P < 0.0001). Success rates were 83% and 91%, respectively, after primary and revision surgeries. Complications were transient with minor consequences in 80% of cases, but could impact quality of life when lasting.ConclusionsThese results support the validity of the French versions of HFS-8 and HFS-30. Microvascular decompression is a safe and effective treatment for hemifacial spasm, and these scales are reliable tools to assess postoperative quality of life.     

Displasia septoóptica: alteraciones oftalmológicas en una serie de 5 casos

Septo-optic dysplasia (SOD) is a rare congenital condition of unknown cause, with a characteristic triad that includes optic nerve hypoplasia, pituitary function abnormalities and midline brain defects, in addition to a broad spectrum of symptoms and associations.A total of five clinical cases are presented, four of which met the complete classic triad. All of them showed a wide variety of ophthalmological, endocrinological and neurological alterations.Within the ophthalmological spectrum of SOD, papillary hypoplasia and ocular motility alterations (nystagmus, strabismus) stand out. Other less frequent ones may also appear, such as pupillary alterations, microphthalmia and coloboma.Given the suspicion of SOD, brain MRI scan should be performed, as well as consultation with the paediatric department in order to complete the study and indicate, if necessary, systemic treatment.