Photoparoxysmal responses in non-epileptic children in long-term follow-up.

OBJECTIVES: To evaluate the photoparoxysmal responses (PPR) in non-epileptic children and adolescents in long-term follow-up. MATERIALS AND METHODS: We studied 14 non-epileptic children who showed PPR without any other electroencephalographic (EEG) abnormalities. RESULTS: One subjects was lost after 1 year of follow-up. At the final follow-up, four of the 13 patients (approximately 30%) did not show any PPR or other epileptic discharges, while in other children PPR continued to be present. The age of the disappearance of PPR in these four patients ranged from 1.1 to 5.9 years from the first evaluation. No patients suffered from epileptic seizures during the whole period of follow-up. CONCLUSION: Our study confirms that PPR can be present in the EEG of non-epileptic children and adolescents and demonstrates that this EEG change is not related to the presence of seizures and must not be considered a marker for the developing of epilepsy.

Effects of antiepileptic drugs on evoked potentials in epileptic children.

To evaluate the visual and auditory function in children and adolescents who are undergoing monotherapy with sodium valproate, carbamazepine, and phenobarbital visual-evoked potentials and brainstem auditory-evoked potentials were measured in 58 epileptic patients (30 males and 28 females), ages 13.7 +/- 6.9 years. Fifty healthy sex- and age-matched children served as controls. The measurements were performed before the beginning of therapy and after 12 months. Before the beginning of therapy, there were no significant differences in visual- and auditory-evoked potentials between the control group and the three groups of epileptic children. After 12 months of therapy, patients treated with carbamazepine demonstrated a significant (P < 0.001) increase of P100 latencies when compared with baseline data and control values; moreover, these patients exhibited a significant increase of peak latencies of waves I-III-V and interpeak interval I-V at auditory second evaluation. The patients treated with sodium valproate manifested a significant (P < 0.05) increase in VEP P100 latencies. On the contrary, children receiving phenobarbital did not manifest any significant abnormality at visual- and auditory-evoked potentials measurements. Our study demonstrates that for patients treated with carbamazepine and sodium valproate, an electrophysiologic dysfunction of visual and auditory sensory pathways can be present after 12 months of treatment.

Discontinuation of anticonvulsant therapy in children with partial epilepsy.

To evaluate when it is possible to discontinue anticonvulsant treatment in children with cryptogenic partial epilepsy, the authors studied 89 epileptic children divided into two groups: Group A, 45 children whose therapy was discontinued after 1 year from the last seizure; and Group B, 44 children whose therapy was stopped after 2 years from the last seizure. After 5 years of follow-up, the recurrence rate was similar in the two groups of patients (Group A, 28.8%; Group B, 25%). It is safe to discontinue the anticonvulsant therapy in children with cryptogenic partial epilepsy who were seizure free for only 1 year.

Predictive value of EEG monitoring during drug withdrawal in children with cryptogenic partial epilepsy.

In order to evaluate the predictive value of the interictal EEG after discontinuation of anticonvulsant therapy in children with cryptogenic partial epilepsy, a prospective study was carried out on 84 children and adolescents who had been seizure-free for at least 2 years. Twenty-four children (28.6%) presented one or more relapses. EEG monitoring during drug withdrawal showed abnormalities in 67% of the patients (16/24) who relapsed with seizures, and in 10% of the patients (6/60) who did not relapse. Our study suggests that in children who have suffered from partial epilepsy, the detection of paroxysmal abnormalities during drug withdrawal, in a previously normal EEG is a risk factor for recurrence of seizures. It is therefore advocated that periodic EEG monitoring be carried out during the drug withdrawal period, because the presence of EEG abnormalities is associated with a high probability of seizures occurring during or after drug discontinuation.

Febrile convulsions after 5 years of age: long-term follow-up.

In order to examine the natural history of febrile convulsions occurring after 5 years of age, we studied 44 children in whom febrile convulsions persisted after 5 years of age (group 1) and compared their development of unprovoked seizures with a group of 195 children in whom febrile convulsions occurred before 5 years of age (group 2). All subjects of group 1 were re-evaluated at the mean age of 13.4+/-1.7 years. The children in group 2 were followed up until they reached the same mean age as children in group 1 (13.1+/-2.3 years). In group 1, we found a higher percentage of unprovoked seizures than in children with febrile convulsions with onset before 5 years of age (18.1% vs 7.4%, P < .05). Our data suggest that children with febrile convulsions after 5 years of age probably must be considered as a group of patients at risk of developing unprovoked seizures.

Benign monomelic amyotrophy of lower limb: report of three cases.

Three patients with wasting confined to a single lower limb are reported. The characteristic features were: sporadic occurrence, insidious onset with slow progression and in 2 cases arrested course for at least 4 years, wasting out of proportion with disability, absence of sensory, pyramidal tract or bulbar signs. CK, motor and sensory conductions, and lumbar MRI were normal. Muscle CT showed selective loss of muscle tissue and fat replacement in posterior leg muscles. Quantitative electromyography and histologic findings revealed neurogenic features not only in the affected legs, but also in clinically uninvolved limbs. Monomelic amyotrophy of lower limb is a variant of spinal muscular atrophy with a benign course. However, as in the early stages of the disease there are no distinctive clinical or laboratory findings with other motor neuron diseases, the diagnosis of monomelic amyotrophy may be made only retrospectively after a prolonged observation.

F response in vascular and degenerative upper motor neuron lesions.

The F response represents the recurrent discharge of a small percentage of the motoneuron pool activated antidromically by any single impulse delivered to the nerve. We studied F waves from median nerve stimulation in 22 controls, in 30 patients with spasticity after cerebrovascular accident (CVA), and in 4 patients with familial spastic paraplegia (FSP). The following parameters were analyzed: median nerve conduction velocity, median nerve M response amplitude (M), average amplitude of 16 F responses (F16); persistence of F response (Fp) defined as the percentage of measurable responses to 16 stimuli, average amplitude of F response expressed as percentage of maximal M amplitude: (F16/M%). Results showed that Fp, F16 and F16/M% values were significantly increased on the spastic side of CVA patients and in FSP. Our findings indicate that after upper motor neuron lesions (whatever etiology and course) a change in the frequency of recurrent discharge and/or in the total number of lower motor neurons capable of backfiring occurs. Therefore, F response reflects the hyperexcitability state of the lower motor neurons in spasticity.

Orthodromic median and ulnar fourth digit sensory conductions in mild carpal tunnel syndrome.

Because the fourth digit (D4) has a dual innervation, median and ulnar D4 sensory conduction velocity (SCV) comparison may be useful in diagnosing the carpal tunnel syndrome (CTS). We studied 50 control hands and 41 hands with recent onset symptoms and signs of CTS but normal median distal motor latency and normal SCV from the second digit (D2). In CTS, D4 SCV was significantly slower than D2 SCV and D4 median and ulnar sensory conduction difference was abnormal in 38 hands (92%). In 36 CTS hands (87%), but in no control hand, a double peak potential could be recorded over the median after D4 stimulation providing an immediate visual confirmation of the diagnosis of CTS. Comparing median and ulnar D4 SCV is a very sensitive method to detect early or mild CTS and should be used whenever conventional electrodiagnostic studies are normal or borderline.

[The sympathetic skin response: neurophysiological basis, normal values, clinical applications]. / La riposta simpatica cutanea: basi neurofisiologiche, valori normativi, applicazioni cliniche.

The sympathetic skin response (SSR) represents the momentary change in skin potential reflexively evoked by a variety of arousal stimuli. Although sudomotor unmyelinated fibres are the final efferent pathway of SSR, little is known about the afferent and central components. SSR was recorded using different classes of stimuli in 20 controls, 15 peripheral neuropathy and 13 stroke patients. In controls SSR latencies changed significantly with different recording sites but not with different stimulation sites. Additionally, ischemic conduction block of the arm abolished SSR recorded at the hand after median nerve stimulation. In 1 patient with subacute ganglionitis and in 3 with demyelinating neuropathies the SSR could be elicited with deep inspiration but not by electric stimulation. These results suggest that myelinated fibres serve as afferents for SSR. In stroke patients SSR was absent bilaterally after stimulation of the paralyzed side but present after stimulation of the normal one. Therefore in humans the cortex seems to have a suprasegmental excitatory influence on SSR. The above findings imply that an unobtainable SSR by electric stimulation may be due not only to dysfunction of the autonomic efferent nerve fibers, but also to involvement of sensory afferents or suprasegmental structures.

Orthostatic tremor: report of two cases and an electrophysiological study.

Two patients with legs tremor present on standing, but none on walking or sitting, are reported. Tremor was not exclusive or orthostatism and was also evoked by strong tonic contraction of leg muscles. Synchronous EMG bursts were recorded in antagonistic muscle groups at 8-10 Hz in the first patient and at 16 Hz in the second. EMG activity was synchronous in corresponding muscles of both legs. The occurrence of EMG activity was not influenced by stimulation of nerve afferent fibers. We suggest that this movement disorder may be an exaggeration of physiological tremor due to synchronization of motor units by spontaneous oscillations in central structures.

Neurophysiological studies of L-acetylcarnitine administration in man.

Systemic administration of L-acetylcarnitine HCl (LAC) increases in human subjects the amplitude of visual evoked potentials (VEPs) obtained with patterned elements of 7.5 min of visual angle, of steady-state VEPs obtained with intermittent luminous stimulation, of EEG theta, alpha and beta bands. The latency of the "cognitive" P300 potential obtained with an auditory "oddball" paradigm was also reduced by LAC injection, while the amplitude of this potential was increased. These results were obtained in control volunteers and in patients affected by different forms of dementias. The modifications induced by LAC appear 10-15 min after the i.v. injection and last for 50-90 min. These results parallel previously described findings of animal experiments and suggest an effect of LAC on cholinergic neurotransmission.