The development of the subplate and thalamocortical connections in the human foetal brain

The aim of this review is to present clinically relevant data on prenatal development of thalamocortical connections in the human brain. The analysis is based on extensive Zagreb Neuroembryological Collection, including more than 500 prenatal human brains stained with various classical neurohistological, as well as modern histochemical and immunohistochemical methods. The connection of thalamocortical axons during the ‘waiting’ period with transient cortical subplate zone and subsequent synaptic engagement in the cortical plate is the main connectivity event in the late foetus and preterm infant. This connectivity is the structural substrate for the endogeneous subplate and sensory‐driven circuitry generating transient electrical phenomena and may represent a transient network in the developmental history of consciousness. Conclusion: Findings presented in this review should be considered in the management of pain in preterm infants, in searching for the vulnerability of the subplate zone in diagnostic procedures using the in vivo MRI and in revealing the developmental origin of cognitive and mental disorders.     

The clinical importance of variations in the surgical anatomy of the superficial peroneal nerve in the mid-third of the lateral leg

The superficial peroneal nerve (SPN) provides fundamental motor and sensory innervation to the leg and foot. A variety of surgical procedures is performed in the vicinity of this nerve, requiring that the surgeon be familiar with its specific anatomy. We dissected 111 legs to define the anatomic position of the SPN and found that the nerve had 4 distinct variations in location. In 77 (69.4%) specimens, the nerve coursed within the lateral compartment of the leg, while in 18 (16.2%) of the legs, the nerve split and contained branches in both the lateral and anterior compartments. The nerve in 7 (6.3%) legs was found within the intermuscular septum, and in 9 (8.1%) of the specimens, the SPN traveled only within the anterior compartment. These results confirm 4 anatomic variants of the SPN, which will aid surgeons in locating the nerve in the lateral aspect of the leg.     

Neurologic manifestations in primary Sjögren syndrome: a study of 82 patients

Neurologic involvement occurs in approximately 20% of patients with primary Sj?gren syndrome (SS). However, the diagnosis of SS with neurologic involvement is sometimes difficult, and central nervous system (CNS) manifestations have been described rarely. We conducted the current study to describe the clinical and laboratory features of SS patients with neurologic manifestations and to report their clinical outcome. We retrospectively studied 82 patients (65 women and 17 men) with neurologic manifestations associated with primary SS, as defined by the 2002 American-European criteria. The mean age at neurologic onset was 53 years. Neurologic involvement frequently preceded the diagnosis of SS (81% of patients). Fifty-six patients had CNS disorders, which were mostly focal or multifocal. Twenty-nine patients had spinal cord involvement (acute myelopathy [n = 12], chronic myelopathy [n = 16], or motor neuron disease [n = 1]). Thirty-three patients had brain involvement and 13 patients had optic neuropathy. The disease mimicked relapsing-remitting multiple sclerosis (MS) in 10 patients and primary progressive MS in 13 patients. We also recorded diffuse CNS symptoms: some of the patients presented seizures (n = 7), cognitive dysfunction (n = 9), and encephalopathy (n = 2). Fifty-one patients had peripheral nervous system involvement (PNS). Symmetric axonal sensorimotor polyneuropathy with a predominance of sensory symptoms or pure sensory neuropathy occurred most frequently (n = 28), followed by cranial nerve involvement affecting trigeminal, facial, or cochlear nerves (n = 16). Multiple mononeuropathy (n = 7), myositis (n = 2), and polyradiculoneuropathy (n = 1) were also observed. Thirty percent of patients (all with CNS involvement) had oligoclonal bands. Visual evoked potentials were abnormal in 61% of the patients tested. Fifty-eight patients had magnetic resonance imaging (MRI) of the brain. Of these, 70% presented white matter lesions and 40% met the radiologic criteria for MS. Thirty-nine patients had a spinal cord MRI. Abnormalities were observed only in patients with spinal cord involvement. Among the 29 patients with myelopathy, 75% had T2-weighted hyperintensities. Patients with PNS manifestations had frequent extraglandular complications of SS. Anti-Ro/SSA or anti-La/SSB antibodies were detected in 21% of patients at the diagnosis of SS and in 43% of patients during the follow-up (mean follow-up, 10 yr). Biologic abnormalities were more frequently observed in patients with PNS involvement than in those with CNS involvement (p < 0.01). Fifty-two percent of patients had severe disability, and were more likely to have CNS involvement than PNS involvement (p < 0.001). Treatment by cyclophosphamide allowed a partial recovery or stabilization in patients with myelopathy (92%) or multiple mononeuropathy (100%). The current study underlines the diversity of neurologic complications of SS. The frequency of neurologic manifestations revealing SS and of negative biologic features, especially in the event of CNS involvement, could explain why SS is frequently misdiagnosed. Screening for SS should be systematically performed in cases of acute or chronic myelopathy, axonal sensorimotor neuropathy, or cranial nerve involvement. The outcome is frequently severe, especially in patients with CNS involvement. Our study also underlines the efficacy of cyclophosphamide in myelopathy and multiple neuropathy occurring during SS.     

Chronic partial sleep deprivation reduces brain sensitivity to glutamate N-methyl-D-aspartate receptor-mediated neurotoxicity

It has been hypothesized that insufficient sleep may compromise neuronal function and contribute to neurodegenerative processes. While sleep loss by itself may not lead to cell death directly, it may affect the sensitivity to a subsequent neurodegenerative insult. Here we examined the effects of chronic sleep restriction (SR) on the vulnerability of the brain to N‐methyl‐d ‐aspartate (NMDA)‐induced excitotoxicity. Animals were kept awake 20 h per day and were only allowed to rest during the first 4 h of the light phase, i.e. their normal circadian resting phase. After 30 days of SR all rats received a unilateral injection with a neurotoxic dose of NMDA into the nucleus basalis magnocellularis (NBM). Brains were collected for assessment of damage. In the intact non‐injected hemisphere, the number of cholinergic cells in the NBM and the density of their projections in the cortex were not affected by SR. In the injected hemisphere, NMDA caused a significant loss of cholinergic NBM cells and cortical fibres in all animals. However, the loss of cholinergic cells was attenuated in the SR group as compared with the controls. These data suggest that, if anything, SR reduces the sensitivity to a subsequent excitotoxic insult. Chronic SR may constitute a mild threat to the brain that does not lead to neurodegeneration by itself but prepares the brain for subsequent neurotoxic challenges. These results do not support the hypothesis that sleep loss increases the sensitivity to neurodegenerative processes.     

Dynamic 3D computer-assisted reconstruction of a metallic retrobulbar foreign body for diagnostic and surgical purposes. [Case report of orbital injury with ethmoid bone involvement]

The main goal of our dynamic 3D computer-assisted reconstruction of a metallic retrobulbar foreign body following orbital injury with ethmoid bone involvement was to use 3D-information obtained from standard computed tomography (CT) data to explore and evaluate the nasal cavity, ethmoidal sinuses, retrobulbar region, and the foreign body itself by simulated dynamic computed visualization of the human head. A foreign body, 10 × 30 mm in size, partially protruded into the posterior ethmoidal cells and partially into the orbit, causing dislocation and compression of the medial rectus muscle and inferior rectus muscle. The other muscles and the optic nerve were intact. Various steps were taken to further the ultimate diagnosis and surgery. Thin CT sections of the nasal cavity, orbit and paranasal sinuses were made on a conventional CT device at a regional medical center, CT scans were transmitted via a computer network to different locations, and special views very similar to those seen on standard endoscopy were created. Special software for 3D modeling, specially designed and modified for 3D C-FESS purposes, was used, as well as a 3D-digitizer connected to the computer and multimedia navigation through the computer during 3D C-FESS. Our approach achieves the visualization of very delicate anatomical structures within the orbit in unconventional (non-standard) sections and angles of viewing, which cannot be obtained by standard endoscopy or 2D CT scanning. Finally, virtual endoscopy (VE) or a ‘computed journey’ through the anatomical spaces of the paranasal sinuses and orbit substantially improves the 3D C-FESS procedure by simulating the surgical procedure prior to real surgery.