What might cervical vestibular–evoked myogenic potential abnormalities mean in essential tremor?

Aim/background

Essential tremor (ET) is one of the most common movement disorders. However, its pathogenesis is unclear. Human vestibular reflexes are essential not only for gait and posture but also for goal-directed voluntary movements. In this study, cervical vestibular–evoked myogenic potentials (cVEMPs), the electrophysiological equivalent of the vestibulo-collic reflex was studied in ET patients to understand the interaction between the tremor network and the vestibular neural pathways.

Methods

cVEMPs were recorded in 40 ET patients and 40 age and sex-matched healthy controls (HCs). The latencies of peaks p13 and n23 and peak-to-peak amplitude of p13-n23 were measured.

Results

There was no statistically significant difference between the p13 latencies of the HC and ET groups (p 0.79 and p 0.23 for the right and left sides respectively). n23 latency was shortened bilaterally in the ET group (p 0.009 and p 0.02 for the right and left sides respectively). p13-n23 amplitudes of the ET patients were bilaterally reduced when compared with the HC (p <0.001 and p 0.001 for the right and left sides respectively).

Conclusion

Information provided by vestibular afferents is crucial in the control of voluntary movements in humans. Despite this silent but significant effect, the role of the vestibular system in movement disorders is often overlooked. In this study, it was found that cVEMP responses reflecting the activity of the vestibulo-collic pathway were affected in ET which can be either caused by dysfunctional structures or pathways responsible from ET or an additional disorder of vestibular information processing in these patients.

     

NEUROPSYCHOLOGIC SEQUELAE IN THE LONG-TERM SURVIVORS OF CHILDHOOD ACUTE LYMPHOBLASTIC LEUKEMIA

The neurotoxicity of either systemic chemotherapy or central nervous system prophylaxis was studied in 19 children treated for acute lymphoblastic leukemia (ALL). They had completed ALL therapy at least a year before and survived more than 5 years after diagnosis. The duration between age at diagnosis and age at investigation was 8.6 2.7 years (5-15 years). Neuropsychologic tests, cranial magnetic resonance imaging (MRI), and evoked potentials (EP) were studied. Seventeen healthy siblings were taken as a control group. Emotional evaluation was done using the childhood depression inventory and Beck depression inventory. Cognitive functions were evaluated using Wechsler's Intelligence Scale for Children-Revised (WISC-R) or the Wechsler's Adult Intelligence Scale-Revised (WAIS-R) tests, which were adapted to Turkish children. Performance and total IQ scores (94.0 16.8 and 92.2 16.5) were significantly low as compared to the control group (112.1 18.9 and 105.4 14.2) (p=.007 and p=.02). Abnormal MRI findings were found in 33.3% (6/18). Three out of 18 patients (16.6%) had abnormal auditory while 5 out of 17 patients (29.5%) displayed abnormal visual EPs. Abnormal findings in MRI, cognitive examination, and electrophysiologic testing were not associated with age at diagnosis, radiotherapy doses, intermediate/high-dose systemic methotrexate administration or central nervous system involvement. But more patients must be studied to demonstrate discrete outcomes of neurotoxicity in long-term survivors of childhood leukemia.     

Evaluating cognitive functions with visual and auditory number assays and P300 in children with epilepsy

This study was planned to evaluate cognitive functions, especially attention and immediate recall, in children with epilepsy by using P300 and neuropsychological tests, which included visual and auditory number assays. Fifty five patients with partial seizures, 45 patients with generalized seizures and 20 patients with intractable seizures were enrolled in the study. Twenty five healthy children were taken as the control group. The results were as follows: 1. P300 latencies were significantly longer in the intractable and partial groups when compared with the control subjects. 2. The duration of epilepsy, seizure frequency, cerebral imaging pathologies were not significantly correlated with delayed P300 latencies. 3. The results of the visual and auditory number assays test showed significant abnormalities when each of the three groups were compared with the normal controls. 4. Though some subgroups of the neuropsychological tests were correlated with the P300 latencies, an overall significant correlation was not present between them. So, we suggest that neuropsychological tests are more convenient for the assessment of cognitive functions in children with epilepsy than the P300 recordings.     

Visual evoked potentials in children with occipital epilepsies

The objectives of this study are to see if any visual evoked potential (VEP) differences are present in two forms of occipital epilepsy, childhood epilepsy with occipital paroxysms (CEOP) and symptomatic occipital epilepsy (SOE) with respect to etiology, as CEOP is a benign age- and localization-related idiopathic epilepsy while SOE is a symptomatic form. Nineteen patients with CEOP and 13 patients with SOE were included in the study and P100 potential latency and amplitude values obtained from these patients were compared with the values recorded from normal controls. The amplitude values recorded from the patients with CEOP were significantly high (P=0.033). P100 potential latency values recorded in patients with SOE were significantly long (P=0.028). High amplitude VEP responses were mostly attributed to hyperexcitability of the occipital cortical structures whereas prolonged latency P100 responses were attributed to occipital structural changes.     

Ptosis and Elevation Paresis Due to Mesencephalic Infarction

Lesions located in the anterior cavernous sinus or posterior orbit are known to cause divisional oculomotor palsy. We herein report a patient with fascicular infarction causing superior division paresis of the nerve.     

Can verapamil be effective in controlling vertigo and headache attacks in vestibular migraine accompanied with Meniere’s disease? A preliminary study

Journal of Neurology -     

Trigeminocervical reflexes elicited by stimulation of the infraorbital nerve: head retraction reflex.

In the current study, the effects of stimulation of the infraorbital nerve (ION) on the trigeminocervical reflexes (TCRs), recorded from the posterior neck muscles, was investigated and the results were compared with the results recorded by stimulation of the supraorbital nerve (SON). TCRs obtained by stimulation of the ION was evaluated as the electrophysiologic counterpart of the head retraction reflex. Twenty normal control subjects, 10 men and 10 women, were enrolled in the study. The SON and the ION were stimulated by using a bipolar surface electrode. Results were recorded by using either concentric needle electrodes inserted into the semispinalis capitis muscle at the level of the third or fourth cervical vertebra or by surface electrodes placed at the C3 and C7 vertebrae on the midline. It was found that stimulation of the supraorbital and infraorbital branches of the trigeminal nerve had different reflexive effects on the posterior neck muscles. A stable positive (or negative-positive) wave, with a very early latency and high amplitude was always recorded after maximal stimulation of the ION, which could never be detected by stimulation of the SON. The C3 response of the TCR, evoked by SON stimulation was always evoked, by stimulation of the ION, at a low threshold. These findings suggest that the head retraction reflex is composed of two phases: inhibitory and excitatory. The early, fixed positive wave represents the general inhibition of the cranial and neck muscles, just before withdrawal of the face and head, from unexpected stimuli, which precedes the dense C3 response, demonstrating activation of the posterior neck muscles.     

The effects of the cerebral,cerebellar and vestibular systems on the head stabilization reflex

The head stabilization reflex (HSR) is a brain stem reflex which appears in the neck muscles in response to sudden head position changes and brings the head to its previous position. The reflex mechanism has not been understood. The afferent fibers come from cervical muscle spindles, vestibular structures, and the accessory nerve, the efferents from the accessory nerve. In this study, we aim to investigate the roles of supraspinal neural structures and the vestibular system on the HSR. The patient group consisted of 86 patients (33 cerebral cortical lesion, 14 cerebellar syndrome and 39 vestibular inexcitability or hypoexcitability); the control group was composed of 32 healthy volunteers. Concentric needle electrodes were inserted into the sternocleidomastoid muscle (SCM) and the accessory nerves were stimulated with the electrical stimulator. A reflex response of about 45–55 ms was obtained from the contralateral SCM muscle. 50 % of cases had bilateral loss whereas 37 % of cases with unilateral cerebellar lesions had an ipsilateral reflex loss. Bilateral HSR loss was detected in 84 % of cases with bilateral cerebellar lesions. Bilateral reflex loss was observed in 70 % of patients with unilateral cortical lesions and 94 % of those with bilateral vestibular dysfunction. Ipsilateral HSR loss was observed in 55 % of cases with unilateral vestibular dysfunction. It was discovered that supraspinal structures and the vestibular system may have an excitatory effect on HSR. This effect may be lost in supra-segmental and vestibular dysfunctions. The localization value of HSR was found to be rather poor in our study.