E. Favale

Anticonvulsant effect of fluoxetine in humans

We report an unblinded, open-label, add-on trial of fluoxetine, a selective serotonin reuptake inhibitor, in 17 patients with complex partial seizures with and without secondary generalization (mean follow-up duration, 14 plus minus 1.1 months). Six patients showed complete disappearance of their daily seizures; in the others the seizure frequency was lowered by 30%. No patient reported side effects. NEUROLOGY 1995;45: 1926-1927

Clinical effectiveness of lamotrigine and plasma levels in essential and symptomatic trigeminal neuralgia.

This paper reports on the effectiveness of oral lamotrigine in 15 patients suffering from “essential” trigeminal neuralgia and in five patients suffering symptomatic trigeminal neuralgia concomitant with multiple sclerosis. We recorded objective and subjective pain ratings and correlated them to daily dosage (400 mg maximum) and plasma levels of the drug. We detected pain relief proportional to daily dosage and to drug plasma levels. Eleven of the cases affected by the “essential” form of neuralgia showed complete pain relief on reaching their maximum daily dosage. All cases affected by the symptomatic form had complete pain relief. We could detect no changes from these results by the end of the follow-up period (3 to 8 months after the study ended).

Epileptic seizures in cerebral arterial occlusive disease.

The occurrence of epileptic seizures was investigated in 141 patients with angiographically proven carotid or MCA occlusive disease. Epileptic seizures occurred some time during the clinical course of the disease in 17.3% of carotid patients and in 10.8% of MCA patients, being mainly represented by partial motor seizures. The pattern of occurrence of seizures in the natural history of cerebral arterial disease was different in the two groups. In the carotid group, epilepsy was the presenting symptom in 6.7% of patients, whereas no MCA patient had seizures prior to the appearance of a neurological deficit. Since epileptic seizures may complicate an otherwise asymptomatic carotid obstruction, angiography should be performed whenever the other standard investigations, including CT-scan, fail to reveal the cause of late-onset epilepsy.

The anticonvulsant effect of citalopram as an indirect evidence of serotonergic impairment in human epileptogenesis.

Some evidence would indicate that a serotonergic deficit may be involved in epileptogenesis. A preliminary trial of citalopram, a selective inhibitor of serotonin reuptake, was carried out. Citalopram 20mg/day was given to 11 non-depressed patients with poorly controlled epilepsy as an add on treatment with an open label design for 8-10 months. The median seizure frequency dropped by 55.6% in the whole group, with nine patients improving by at least 50%. No adverse reactions occurred with the exception of mild drowsiness. There were no changes of post-treatment as compared to pre-treatment AED serum concentrations. Although controlled studies are required to confirm the anticonvulsant effect of citalopram, these findings may be regarded as an indirect evidence of serotonergic impairment in human epileptogenesis.

Proprioceptive modulation of somatosensory evoked potentials during active or passive finger movements in man.

The effects of active and passive finger movements on somatosensory potentials evoked by stimulation of the median nerve at the wrist or of finger I were investigated in 15 healthy volunteers. As compared to the resting condition, both active and passive movements of the stimulated hand fingers induced a marked reduction in the amplitude of the primary cerebral response (N20-P25 complex) as well as of the N17 SEP component, which is supposed to reflect the activity of the thalamo-cortical radiation. The following cerebral SEP components, within 100 ms after the stimulus, were also depressed during motor activity. Neither N11 nor N13 components of the cervical response, reflecting the activation of dorsal columns and dorsal column nuclei respectively, were modified. The SEP changes induced by active or passive movements were absent after ischaemic block of large group I afferent fibers from the hand, thus suggesting the relevance of the feedback generated by such peripheral afferents during movement. The results indicate that the activation of peripheral receptors (probably muscle spindle endings) during both active and passive finger movement would induce a gating effect at both cortical and subcortical (thalamic) level, which might modulate selectively the different sensory inputs to the cortex.

Somatic afferent transmission and cortical responsiveness during natural sleep and arousal in the cat

Abstract Both peripherally and centrally evoked somatic responses vary greatly in amplitude according to the level of vigilance. This effect is due both to modifications of afferent transmission along the somatic pathways and to variations in responsiveness of the cortical neurones. In particular: 1. (a) the afferent transmission at the level of the 1st station (gracilis and cuneatus nuclei) does not seem to be affected by the depth of sleep, being unchanged during deep sleep as compared to light sleep; during arousal it may vary greatly according to concomitant behavioural changes; 2. (b) the afferent transmission at the level of the 2nd station (nucleus ventro-postero-lateralis of the thalamus) is constantly affected by the depth of sleep, being maximal during deep sleep; during arousal it can appear either facilitated or depressed according to the depth of the preceding spell of sleep; 3. (c) somatic cortical responsiveness is maximal during light sleep, being apparently depressed during deep sleep and arousal.

Abnormalities of parietal and prerolandic somatosensory evoked potentials in Huntington's disease

Cervical, parietal and prerolandic somatosensory evoked potentials (SEPs) to median nerve stimulation at the wrist were recorded with an earlobe reference in 24 patients with Huntingtons disease (HD) and in 24 age-matched normal controls. Cortical responses of abnormal wave form and reduced amplitude were constantly observed in HD patients. SEP changes affected more severely the prerolandic (P22/N30) pattern, which could not be recognized in two-thirds of patients, than the parietal (N20/P27) pattern, which could be identified in all cases. The N20 latency and the central conduction time (N13-N20 interval) were significantly increased. The occurrence of abnormalities of central conduction and of a predominant involvement of the prerolandic SEP pattern suggests an impairment of impulse transmission along the somatosensory lemniscal pathway at subcortical, possibly thalamic, level in HD.

Electrical stimulation of the motor tracts in cervical spondylosis.

Motor action potentials evoked by percutaneous electrical stimulation of the scalp and of the cervical (or lumbar) vertebral region were recorded from the biceps, thenar and tibialis anterior muscles in 30 patients with cervical spondylosis. Twelve normal controls were matched for age and height. Abnormalities of central motor conduction (absence or increased central delay of cortical responses) for at least one muscle were observed in all (but one) the patients with myelopathy alone or combined with radiculopathy. An increase in latency of the responses evoked by cervical stimulation occurred in 40% of patients with radiculopathy or myelo-radiculopathy. Changes of motor conduction occurred even in the absence of abnormalities of somatosensory evoked potentials, while the opposite was never observed. Direct stimulation of the motor tracts may be of value in the functional assessment of the motor pathways in cervical spondylosis.

Subcortical and cortical responses following infraorbital nerve stimulation in man

Scalp responses following stimulation of the infraorbital nerve have been recorded in awake and anaesthetized subjects from non-cephalic (NCR) and vertex (VR) reference derivations. In awake subjects, after 3 very early potentials (W1, W2 and W3), 4 small components (P4, N5, P6 and N7) with widespread distribution have been constantly recorded from NCR derivations. Sometimes a further component, named N10, could be recorded in VR derivations on the scalp contralateral to the stimulus in the absence of earlier events. Large and inconstant waves were recorded following N7 in NCR and N10 in VR derivations. The muscular origin of these waves was demonstrated by simultaneous records taken from scalp and muscles. Records from NCR derivations in anaesthetized subjects showed that wave N7 was followed by a further event (N10) localized on the scalp contralateral to the stimulus and by a few slow waves. Wave N10 could also be recorded, in the absence of earlier events, from the VR derivation contralateral to the stimulus. All the responses recorded in these patients could be considered of neurogenic origin because curarization abolished any reflex activation of muscles. All the waves following W3 are of postsynaptic nature and, on the basis of their distribution and latency, we suggest that P4, N5, P6, N7 and N10 have their respective origins in the trigeminal nucleus, trigeminal lemniscus, thalamus, thalamic radiation and cortical projection of the stimulated area. It was also demonstrated that stimulation of lips and gums fails to evoke any neural event recordable from the scalp.

New subcortical components of the cerebral somatosensory evoked potential in man

Two new components of the human SEP upon stimulation of the contralateral median nerve at the wrist have been identified. Such components have been called N16 and N17, according to their polarity and latency. N16 and N17, as well as the N14‐P15 complex, are generated by separate subcortical dipoles. Particularly, they are supposed to be far‐field reflections of the activity of the dorsal columns nuclei or the medial lemniscus (N14‐P15), the thalamus (N16) and the thalamo‐cortical radiation (N17). Moreover, it has been established that N14 is the very first intracranial component of the human SEP, the main peak of S wave and the preceding ones being extracranial in origin.