Topodiagnostic investigations on the sympathoexcitatory brain stem pathway using a new method of three dimensional brain stem mapping

OBJECTIVES: To study the incompletely understood sympathoexcitatory pathway through the human brain stem, using a new method of three dimensional brain stem mapping on the basis of digitally postprocessed magnetic resonance imaging (MRI). METHODS: 258 consecutive patients presenting with acute signs of brain stem ischaemia underwent biplane T2 and EPI diffusion weighted MRI, with slice orientation parallel and perpendicular to a transversal slice selection of the stereotactic anatomical atlas of Schaltenbrand and Wahren, 1977. The individual slices were digitally normalised and projected onto the appropriate slices of the anatomical atlas. For correlation analysis lesions were imported into a three dimensional model of the human brain stem. RESULTS: 31 of the 258 patients had Horner's syndrome caused by acute brain stem ischaemia. Only four of the patients with Horner's syndrome had pontine infarctions, 12 had pontomedullary lesions, and 15 had medullary lesions. Correlation analysis showed significantly affected voxels in the dorsolateral medulla but not in the pons. A statistical comparison with infarct topology in patients with medullary lesions but without Horner's syndrome indicated that involvement of the medial and ventral part of affected voxels located in the ventrolateral medullary tegmentum was specific for Horner's syndrome. CONCLUSIONS: Based on this first in vivo topodiagnostic study, the central sympathoexcitatory pathway probably descends through the dorsal pons before converging on specific generators in the ventrolateral medullary tegmentum at a level below the IX and X nerve exits.     

Evidence of a specific spinal pathway for the sense of warmth in humans

While research on human sensory processing shows that warm input is conveyed from the periphery by specific, unmyelinated primary sensory neurons, its pathways in the central nervous system (CNS) remain unclear. To gain physiological information on the spinal pathways that convey warmth or nociceptive sensations, in 15 healthy subjects, we studied the cerebral evoked responses and reaction times in response to laser stimuli selectively exciting Adelta nociceptors or C warmth receptors at different levels along the spine. To minimize the conduction distance along the primary sensory neuron, we directed CO(2)-laser pulses to the skin overlying the vertebral spinous processes. Using brain source analysis of the evoked responses with high-resolution electroencephalography and a realistic model of the head based on individual magnetic resonance imaging scans, we also studied the cortical areas involved in the cerebral processing of warm and nociceptive inputs. The activation of C warmth receptors evoked cerebral potentials with a main positive component peaking at 470-540 ms, i.e., a latency clearly longer than that of the corresponding wave yielded by Adelta nociceptive input (290-320 ms). Spinal neurons activated by the warm input had a slower conduction velocity (2.5 m/s) than the nociceptive spinal neurons (11.9 m/s). Brain source analysis of the cerebral responses evoked by the Adelta input yielded a very strong fit for one single generator in the mid portion of the cingulate gyrus; the warmth-related responses were best explained by three generators, one within the cingulate and two in the right and left opercular-insular cortices. Our results support the existence of slow-conducting second-order neurons specific for the sense of warmth.     

Seizures in paediatric Chiari type I malformation: the role of single-photon emission computed tomography

Chiari type I malformation is one of the posterior fossa maldevelopments with which different clinical manifestations have been associated. Seizures have only recently been associated with Chiari type I malformation. This study reports on 4 children with epilepsy (2M, 2F; age range 8-15 y) diagnosed with Chiari type I malformation by brain magnetic resonance imaging (MRI), in whom no cortical structural involvement was observed. In these patients an interictal ethylcysteinate-dimer-single-photon emission computed tomographic (ECD-SPECT) study was performed to define more precisely the relationship between Chiari type I malformation and seizures. In these patients the hypoperfusion area correlated with electroencephalographic (EEG) focal abnormalities. These hypoperfusions may represent the functional aspect of a cerebral microdysgenesis; seizures and EEG epileptic anomalies may also be linked to the complex network connection between cortices and cerebellar hemispheres. A cerebellar hypoperfusion was also detected in two of the four examined patients, indicating a functional or structural involvement. CONCLUSION: Interictal SPECT scans are helpful for the clarification of seizures in patients with Chiari type I malformation.     

Metabolic changes in rabbit lens induced by treatment with dexamethasone

Metabolic changes in the rabbit lens have been studied by means of nuclear magnetic resonance spectroscopy. These changes have been induced by prolonged topical treatment with dexamethasone. Our results demonstrate an increase in sorbitol, sorbitol-3-phosphate, fructose-3-phosphate, glycerol-3-phosphate and glucose-6-phosphate levels and a decrease in glutathione sulphate (GSH) and myo-inositol levels, in agreement with what was observed in lenses from streptozocin-diabetic rats before lens opacity. The hyperglycaemia can only partially explain all these observed biochemical variations. The lack of increase in the intermediates of pentose cycle, such as sedoheptulose-7-phosphate, seems to support the hypothesis of an inhibition of glucose-6-phosphate dehydrogenase by dexamethasone treatment. Finally dexamethasone treatment induces a decrease in GSH. The decreasing or the loss of GSH has been suggested as a possible pathogenic mechanism in the cataract formation.     

Facial nerve functionality after parotid tumors surgery

The purpose of this study is to show the connection among tumor histology, surgical treatments and facial nerve postoperative functionality. A retrospective review was conducted on 69 patients with benign and malignant parotid tumors: they underwent surgical treatment for benign and malignant parotid tumors at the Maxillofacial Division of Rome University "La Sapienza" from 1988 to 1997. In our series of patients, we performed conservative superficial parotidectomy, conservative total parotidectomy and radical parotidectomy. Tumor enucleation was reserved for those neoplasms with a limited and restricted mass. The surgical approach was based on mass extension and on histopathologic features. Our findings showed that a careful and a timely diagnosis is very important in order to select a conservative surgical treatment for benign and intermediate grade of malignancy tumors with limited dimensions. Most aggressive histological types, and large mass dimensions require a radical treatment with consequent facial nerve postoperative dysfunctions. Our experience demonstrates that this surgical approach provides a very high rate of success in the cure of tumors and a low rate of facial nerve postoperative dysfunctions.     

Herpetic meningoencephalitis in infants. Study of 7 cases]

Seven children with herpes meningoencephalitis aged between 14 days and 13 months were studied. The herpes infection was confirmed by isolation of herpes virus from the CSF (one case), from the brain (one case), and in the 5 remaining cases by serology. The strains isolated were herpes type 2. The clinical features of herpes meningoencephalitis in the first year of life and the laboratory data are described.     

Messenger RNAs in synaptosomal fractions from rat brain.

Synaptosomal fractions from rat brain have been analyzed with semi-quantitative RT-PCR methods to determine their content of mRNAs coding for presynaptic, postsynaptic, glial, and neuronal proteins. Each mRNA was determined with reference to the standard HPRT mRNA. In our analyses, mRNAs were considered to be associated with synaptosomes only if their relative amounts were higher than in microsomes prepared in a polysome stabilizing medium, rich in Mg(++) and K(+) ions, or in the homogenate. According to this stringent criterion, the following synaptosomal mRNAs could not be attributed to microsomal contamination and were assumed to derive from the subcellular structures known to harbor their translation products, i.e. GAT-1 mRNAs from presynaptic terminals and glial processes, MAP2 mRNA from dendrites, GFAP mRNA from glial processes, and TAU mRNA from neuronal fragments. This interpretation is in agreement with the involvement of extrasomatic mRNAs in local translation processes.     

Trigeminal small-fibre dysfunction in patients with diabetes mellitus: a study with laser evoked potentials and corneal reflex.

OBJECTIVE: To investigate trigeminal small-fibre function in patients with diabetes mellitus. METHODS: In 52 diabetic patients we studied the trigeminal laser evoked potentials after stimulation of the skin bordering the lower lip. In the 21 patients with the severest peripheral nerve damage we also studied the electrically evoked corneal reflex. Both responses are mediated by small myelinated afferents. RESULTS: Laser evoked potentials had a longer mean latency and lower amplitude in diabetic patients than in normal subjects (P<0.005). The abnormality frequency of the laser evoked potentials correlated with the severity of polyneuropathy (P<0.005). In contrast, the corneal reflex was normal. CONCLUSION: Dysfunction of small afferents of the mandibular nerve is frequent in patients with diabetic polyneuropathy. We speculate that the primary cause could be segmental demyelination.