Giovanni Broggi

Depolarization of trigeminal afferents induced by stimulation of brain-stem and peripheral nerves

Summary1.In nembutalized cats the excitability of supraorbital (SO) and infraorbital (IO) primary afferents was tested by microelectrode stimulation within the trigeminal nuclei. SO excitability increased after conditioning stimulation of IO nerve, brain-stem throughout its extent and ipsi- and contralateral fore- and hindlimb nerves. The conditioning curves did not change in decerebrate preparations.2.In decerebrate cats a negative slow potential (trigeminal dorsal root potential, TDRP) was recorded from the isolated sensory trigeminal root following stimulation of contralateral SO nerve, homolateral common radial trunk and brain-stem.3.In nembutalized as in decerebrate cats, a single IO impulse induced in the trigeminal complex a focal synaptic potential (N1-N2-waves) followed by a prolonged (200 msec) slow potential (P-wave). P-waves were also produced by high frequency stimulation of the brain-stem reticular regions. They were positive laterally to the trigeminal nucleus and inverted along a line between nucleus and tract. The N-wave had maximal amplitude in the trigeminal nucleus and became positive at the level of its medial boundary.4.Unit discharges in the trigeminal nucleus responding to IO volley and lemniscal potentials evoked by the same stimulus were depressed by reticular activation following a time course of over 100 msec.5.The results suggest a process of primary afferent depolarization (PAD), of trigeminal fibers induced by stimulations of brain-stem, fore- and hind-limbs nerves and other trigeminal afferents in absence of forebrain and cortical structures.

Study of the Excitability Cycle of the Blink Reflex in Huntington’s Chorea

The trigemino-facial reflex was studied in 7 patients affected by Huntingtons chorea and in 10 patients affected by Parkinsons disease. The results show a different behavior of the habituation phenomenon in the two groups of patients: it is enhanced in the choreic and abolished in the parkinsonian patients. The main changes concern the time course of the second phase (the first inhibitory phase) of the reflex excitability cycle, in fact, the inhibitory phase appears very pronounced and prolonged in huntingtonian patients and reduced or abolished in parkinsonian patients. Some pathophysiological mechanisms involved in the control of the trigeminofacial reflex excitability are discussed with particular regard to the role of the hemispheric structures.

Intention and Action Myoclonus from Thalamic Angioma

Clinical electrophysiological and neuroradiological examination of a case of unilateral intention and action myoclonus is reported. Brachial arteriography revealed an angioma located mainly in the lat

Brain stem-thalamus reciprocal influences in the cat

Abstract Intracellular recordings were made from Mth neurons in acute ‘encephale isole’ preparations during low- and high-frequency BP and Mes stimulation. Low-frequency BP stimulation induced short-latency (1–5 msec) EPSPs on Mth neurons, followed by IPSPs which could also appear in isolation. High-frequency BP activation produced mixed excitatory and inhibitory effects. Low-frequency Mes stimulation mainly induced long-latency and long-lasting IPSPs while high-frequency activation blocked spontaneous firing of Mth neurons with or without increase in membrane potential. Similar effect was seen during high-frequency Mth stimulation. DCN stimulation never affected any of the Mth studied neurons. Control experiments have excluded the co-stimulation of spinothalamic and cerebello-rubro-thalamic pathways. Intracellular injection of hyperpolarizing and depolarizing current showed that BP effects were postsynaptic whereas Mes inhibition was due to removal of excitation (i.e., disfacilitation) on Mth neurons. High-frequency BP stimulation induced an increase of cell firing and reduction of the inhibitory phase in the thalamically induced sequences, while Mes activation reduced the EPSPs without apparent changes of IPSPs. Low- and high-frequency Mth stimulation evoked short-latency (1–4 msec) EPSPs on BP and Mes neurons with an increase of firing which was more evident during high-frequency stimulation. Antidromic invasion in some BP and Mes neurons was also found. The results indicate the existence of a reciprocal brain stem-thalamic linkage which is excitatory in the descending, while it is excitatory and inhibitory in the ascending way from BP regions, and mainly disfacilitatory from the midbrain.

Multisensory convergence and interaction in the pulvinar-lateralis posterior complex of the cat's thalamus

Responsiveness to visual, acoustic and somesthesic stimuli was studied in 260 units recorded within the associative thalamic nuclei of the cat (pulvinar-lateralis posterior complex and posterior group). Of the 123 units responding to one or more stimuli 41 (corresponding to 15% of the total) showed multisensory convergence. Bimodal, visual-somesthesic convergence was the most common finding, occurring in 33 units. Visual-somesthesic inhibitory interaction was observed only in the pulvinar nucleus, suggesting a peculiar synaptic organization of multisensory input to this nucleus.

Familial Idiopathic Basal Ganglia Calcification Exhibiting ‘Dystonia musculorum deformans’ Features

Basal ganglia calcifications have been reported in cases of abnormality of parathyroid glands function showing various clinical manifestations. Two cases of familial idiopathic basal ganglia and possi

Presynaptic inhibition of trigeminal afferent fibres during the rapid eye movements of desynchronized sleep

Durante i movimenti oculari rapidi nel sonno desincronizzato ed al momenta del risveglio si assiste ad un aumento in ampiezza della risposta antidromica evocata nel nervo infraorbitario dalla stimolazione microelettrodica del tratto spinale del trigemino a livello pontino. Tali variazioni suggeriscono un processo di inibizione presinaptica che agisce fasicamente sulle terminazioni afferenti primarie del trigemino.

Self-closing surgical clips for use in pericallosal artery–pericallosal artery side-to-side bypass: Case report

The authors demonstrate the feasibility of a new procedure to create intracranial interrupted microvascular anastomosis. Self-closing nitinol surgical clips were used for a pericallosal artery-pericallosal artery side-to-side bypass in a 52-year-old man harboring an unruptured large aneurysm located on the right A2 segment. The outflow artery was found to arise from the dome of the aneurysm, which was considered unsuitable for stand-alone clip ligation or coil occlusion. After bypass patency was intraoperatively confirmed using near-infrared indocyanine green videoangiography, the aneurysm and feeding artery were embolized with coils and safely occluded. Both postoperative courses were uneventful. The patient was discharged neurologically intact on the 5th postembolization day. Postprocedure angiography demonstrated no ipsilateral aneurysm filling and excellent bilateral distal outflow from the left anterior cerebral artery.

Spinal reflexes in normal unrestrained cats during sleep and wakefulness

I riflessi spinali monosinaptico (MR) e polisinaptico (PR) variano in ampiezza ma sono sempre presenti nella veglia e sonno leggero. Nel sonno profondo il MR e PR sono aboliti; la soglia del MR è innalzata e la potenziazione post-tetanica abolita.

Primary afferent depolarization of trigeminal fibres induced by stimulation of brain stem and peripheral nerves

be obtained if the fibre stimulated belonged to the static type (Figure 1 D). Simultaneous activation of 2 static fusimotor fibres or of 1 dynamic and 1 static fibre converging onto the same spindle ending, gave similar results. On the other hand, at the rates of change of muscle length and fusimotor stimulation frequency used, stimulation of a single dynamic fusimotor fibre, or of 2 converging fibres for that matter, could never increase or even maintain the impulse frequency during muscle shortening (Figure 2 D). The findings thus suggest that the increase in impulse frequency of the primary ending seen during contraction in natural movements requires static fusimotor activation 1 z