Prepulse modulation of the startle reaction and the blink reflex in normal human subjects.

Blink reflexes are usually considered the most representative and consistent response of the auditory startle reaction (ASR), and they are often the only response evaluated in human psychophysiological studies. However, auditory stimuli also induce an auditory blink reflex (ABR), the physiological characteristics and brainstem circuitry of which may be different from those of the ASR. This study aimed to investigate whether there were differences between the orbicularis oculi (OOc) responses elicited with the ABR (OOcABR) and those elicited with the ASR (OOcASR) regarding their behavior to prepulse modulation. For comparison, we also examined the OOc responses to supraorbital nerve stimulation (OOcEBR). Electromyographic responses were simultaneously recorded from the OOc, masseter (MAS) and sternocleidomastoid (SCM) muscles. ABRs were considered when auditory stimuli induced responses limited to the OOc, and ASRs were considered when responses were induced in all muscles recorded from. Prepulse stimuli were either a weak electrical stimulation at the third finger (somatosensory prepulse) or a weak acoustic tone (auditory prepulse) that preceded the response-eliciting stimuli by intervals ranging from 0 to 200 ms. Prepulse effects differed according to prepulse modality, but the OOcABR and the OOcASR were always modulated in the same way. In both responses, somatosensory prepulses induced facilitation from 20 to 50 ms, followed by inhibition beyond 75 ms, and auditory prepulses induced no facilitation but a significant inhibition beyond 30 ms. In the OOcEBR, both somatosensory and acoustic prepulses induced facilitation of R1 and inhibition of R2 beyond 30 ms. Our results suggest that the OOcABR and the OOcASR exhibit the same physiological behavior regarding prepulse modulation. It is hypothesized that prepulse facilitation is due to direct impingement of subthreshold excitatory inputs onto the facial motoneurons while prepulse inhibition results from the engagement of a presynaptic inhibitory circuit in the brainstem.

Effects of a startling acoustic stimulus on reaction time in different parkinsonian syndromes.

BACKGROUND: The functional assessment of the startle circuit is usually done by analyzing the acoustic startle response (ASR). However, a startling acoustic stimulus (SAS) also induces changes in the excitability of neural structures that can be demonstrated by studying the SAS-induced change in the behavior of certain neurophysiologic responses. OBJECTIVE: To examine the effects induced by an SAS on voluntary reaction time in patients with parkinsonian syndromes (StartReact effect) and to compare the results with those obtained in a group of age-matched healthy volunteers. METHODS: Twelve patients with idiopathic PD (IPD), seven patients with progressive supranuclear palsy (PSP), seven patients with multisystem atrophy (MSA), and seven healthy age-matched control volunteers performed a simple visual reaction time task and received SAS together with the "go" signal in random trials. RESULTS: Baseline reaction time was significantly slower in PSP patients than in control subjects and MSA patients. The SAS induced a significant shortening of the reaction time in control subjects and in patients with IPD and MSA, but not in patients with PSP. The percentage of reaction time shortening with regard to the baseline values also differed significantly between PSP patients and the other groups of subjects. The StartReact effect was consistent throughout the experiment and showed reduced habituation with repeated testing. CONCLUSIONS: The results are consistent with an abnormal function of the startle circuit in patients with PSP and agree with previous studies using the ASR. The reduced habituation of the StartReact effect favors its clinical applicability in the assessment of differences between patients with parkinsonian syndromes.

The acoustic startle response is normal in patients with multiple system atrophy.

We investigated the acoustic startle response in eight patients with MSA and compared the results with those from a group of age matched healthy subjects. Onset latency and amplitude of the responses obtained in the orbicularis oculi, masseter and sternocleidomastoid muscles were not different in patients and control subjects. We conclude that, in spite of the pathological derangement described in brainstem reticular nuclei in MSA, the neuronal circuits mediating the auditory startle reflex are functionally preserved.

Habituation of the auditory startle reaction is reduced during preparation for execution of a motor task in normal human subjects.

The generalized acoustic startle reaction is a useful but labile phenomenon that undergoes a relatively rapid habituation with repeated stimuli and can be modified by changes in the environmental context. In the present work, we examined the influence of the experimental set on size, latency and habituation rate of auditory startle reactions in 15 normal volunteers. Series of 5 acoustic startling stimuli were applied on each of the following 4 conditions: (1) at rest in a quiet and dull ambience; (2) at rest but engaged in a busy environment; (3) being prepared to execute a reaction time task; and (4) focussing the attention to an impending visual stimulus. We found that the amplitude of the response to the first stimulus was significantly larger in condition 1, and habituation rate was significantly reduced in condition 3, with respect to all other conditions. The enhancement of the startle reaction in a quiet ambience may result from reduction of the sensory inputs from the environment, which would otherwise act as prepulses and cause a certain degree of inhibition. The reduced habituation rate of the startle reaction with preparation for a reaction time task may be due to a transient block of the cortical inhibitory control on inputs from non-expected sensory afferents. A careful description of the experimental conditions with which the startle reactions are tested is required for meaningful comparison of the results from different laboratories. The possibility to reduce habituation of the startle reaction with preparedness for execution of a motor task has important implications with regard to the applicability of the startle reaction on research and clinical practice.

Lesion of dentatothalamic pathways in severe post-traumatic tremor.

The present study investigates evidence of dentatothalamic pathway lesions in nineteen patients with severe kinetic post-traumatic tremor respectively by magnetic resonance imaging (MRI). Kinetic tremor is thought to be characteristic of lesions of the cerebellar outflow. While this hypothesis is supported by experimental data, neuropathological and neuroradiological findings have been limited. The appendicular tremors were unilateral in 13 patients and bilateral in 6, accounting for 25 instances of tremor. The tremor developed after severe head trauma in 18 patients. These patients had evidence of diffuse axonal injury on MRI. Postural and kinetic tremor was present in all patients, and was accompanied by tremor also present at rest in 14 instances. Multiplanar MRI studies were performed on a high-field MRI system operating at 2.0 T in 13 patients and on intermediate-field strength MRI systems in 6 patients according to a standardized protocol. To detect small deposits of hemosiderin after post-traumatic lesions, the protocol included a heavily T2-weighted spin-echo pulse sequence. Lesions of the dentatothalamic pathways were found in 22 instances. The lesions were classified into different types of according to their distribution. A lesion of the dentate nucleus ipsilateral to the tremor (type 1) was found in one instance (4%), lesions involving the ipsilateral predecussational dentatothalamic pathway (type II and III) were found in 14 instances (56%), and lesions involving the contralateral post-decussational course (type IV) in 7 instances (28%). One patient with a mild head trauma had a lesion of the contralateral thalamus. The lesions appeared as hypointense, hyperintense or mixed. Two of three patients with a parkinsonian-like rest tremor had type IV lesions involving the substantia nigra. The nosological concepts of tremors are discussed. 'Midbrain' tremor may have distinct pathoanatomical lesion sites.

The treatment of posttraumatic tremor by stereotactic surgery. Symptomatic and functional outcome in a series of 35 patients.

The authors report the long-term results of stereotactic surgery for severe posttraumatic appendicular tremor in 35 patients. The tremors developed after severe head trauma in 33 patients (94%) and after mild to moderate head trauma in two (6%). In all but one, the tremor was most evident during activity. The amplitude of the kinetic tremor was greater than 5 cm in 33 patients (94%) and greater than 12 cm in 19 patients (54%). All were severely incapacitated in their daily living activities due to the tremors. The 35 patients underwent 42 stereotactic operations; five patients were reoperated on the same side and two were treated with a bilateral staged procedure. The contralateral zona incerta was the stereotactic target in 12 patients and was targeted in combination with the base of the ventrolateral (oroventral) thalamus in 23 patients. Long-term postoperative follow-up review was obtained in 32 patients (mean follow-up period 10.5 years). Persistent improvement of tremor was noted in 88%. The tremor was absent or markedly reduced in 65%. Functional disability was assessed and quantified with a modified form of an established rating scale for patients with tremor; it was reduced from a mean value of 57% of maximum disability to 37% over the long term (p < 0.001). Follow-up lesion assessment was obtained in 18 patients by multiplanar magnetic resonance imaging and at autopsy in one patient whose death was unrelated to surgery. As in previous studies, the frequency of persistent side effects was relatively high (38%). These consisted mainly of aggravation of preoperative symptoms. The results are compared to those of a total of 55 patients reported from 1960 to 1992. The occurrence of dystonia and dystonic postures is discussed. Stereotactic surgery is a powerful tool to alleviate posttraumatic tremor and to improve functional disability. However, as there is considerable risk of persistent morbidity in patients after severe head trauma, the operation should be restricted to selected cases with disabling tremor.

Evaluation of the effect of treatment on movement disorders in astrocytomas of the basal ganglia and the thalamus.

Twenty patients with movement disorders associated with astrocytomas (grade I-IV according to the WHO tumour classification) of the basal ganglia and the thalamus were evaluated for the effects of treatment. Five patients had more than one movement disorder when the histological diagnosis was verified by stereotactic biopsy. Twelve had tremors, eight hemidystonia, three hemichorea, and one hemichorea/ballismus, and myoclonus respectively. Ten patients died during the follow up period, and for the surviving patients follow up periods ranged from 6-21 years. The movement disorders changed over long periods of time related to therapeutic interventions. CSF shunt operations and percutaneous radiotherapy had no definite effect on the movement disorders. There was a moderate response to medical treatment in a few patients. Stereotactic aspiration of tumour cysts had a marked influence on the movement disorder in two patients, and functional stereotactic surgery abolished tumour induced tremor in one. Interstitial radiotherapy was performed in fifteen patients for treatment of the underlying neoplasm and resulted in different and variable alterations of the movement disorders. These differences may be explained by complex interactions involving structures affected primarily by the tumour, as well as by secondary functional lesions of adjacent structures.

Movement disorders in astrocytomas of the basal ganglia and the thalamus.

In a series of 225 patients with astrocytomas (grades I-IV) of the basal ganglia and the thalamus, 20 had a movement disorder. In all patients the histological diagnosis was verified by stereotactic biopsy. Tremor was observed in twelve patients, dystonia in eight, chorea in three, and chorea/ballismus and myoclonus in one. The tumour involved the thalamus in 16 patients. Corticospinal tract dysfunction was evident in 70% of the patients with movement disorders and in 73% of those without. Demographic, clinical, histological and neuroradiological data of the patients with a movement disorder were compared with the data of patients without. CT data yielded no differences with respect to the involvement of anatomical structures. Movement disorders were significantly associated with low-grade astrocytomas.

Bilateral ballismus in children.

Bilateral ballismus is extremely rare. We found 23 reported cases, and only 2 of these were in children. In older patients the movement disorder is usually due to cerebrovascular disease, but in younger patients a variety of aetiopathological causes may be found. There are few data regarding medical treatment. There have been no previous reports on stereotactic operations. We report on two severely disabled children who underwent stereotactic surgery. A 9-year-old boy suffering from bilateral ballismus after meningoencephalitis was operated on bilaterally (two operations 1 year apart). Another 9-year-old boy, who was suffering from progressive, presumably degenerative, basal ganglia disease, was operated on unilaterally. The nosological and conceptual controversies differentiating bilateral ballismus as a phenomenological entity are reviewed. The therapeutic options, indications, and special problems of stereotactic surgery in these rare cases are discussed.

[Effect of a drug combination on venous capacity]. / Zur Wirkung eines Kombinationspräparates auf die Venenkapazität.

The activity of the fixed combination Phlebodril on the venous hemodynamic system was studied in 20 healthy volunteers. A different reaction was seen. One part of the volunteers showed a significantly reduced venous capacity whereas the other part presented an increase in venous storage ability. This effect especially was observed after application of trimethylhesperidinchalcone, which increases the capillary resistance.

[Changes of venous hemodynamics by thermic stimuli (author's transl)]. / Zur beeinflussbarkeit der venösen Hämodynamik durch thermische Reize.

Measurement of the venous capacity by means of strain-gauge-plethysmography when performed under standardised conditions produces reproducible values in chronic test also. Acutely, the venous capacity of the healthy can be reduced by cold water and increased by warm water appplication. When measuring pressure in the great saphenous vein, which was performed during stress test and after cooling down, a clear improvement of the valvular function in the shank coud be ascertained. The healthy lying down, a distinct increase of the venous tonus takes place after application of cold water. With respect to primary varicosis, in addition to the acute reduction of volume, a chronic training effect, in the sense of a reduction in the venous capacity, significantly can be a convenient means for the treatment of primary varicosis and of less severe forms of chronic venous insufficiency.