Isometric muscle contraction in endocrine myopathies.

Isometric contraction of the adductor pollicis muscle of the thumb was evoked by stimulating the ulnar nerve in 20 normal adults and 58 patients with endocrine disorders. We evaluated mechanical latency, electromechanical latency, contraction time, half relaxation time, isometric twitch force, compound muscle action potential, nerve conduction velocity, and relative refractory period. Mechanical characteristics were altered in diseases of the pituitary, thyroid, and parathyroid glands. The close relationship between thyroid hormone and contractile properties discriminated between hypo- and hyperthyroidism.

Changes of sensory conduction velocity and refractory periods with decreasing tissue temperature in man.

Changes with temperature of maximum sensory nerve conduction velocity as well as absolute and relative refractory periods were tested in 14 human subjects. Corresponding to previously published findings maximum conduction velocity decreased with cooling following a Q10 of +1.4. The absolute and relative refractory periods were increased by cooling, the Q10 being -3.1 and -3.35 respectively. There was a tendency showing a more pronounced temperature effect at low temperatures. The Q10 and the steepness of the regressionline changed at the level of 26.9 degrees C, but were significant for the relative refractory period only.

Hypokalemia shortens relative refractory period of peripheral sensory nerves in man.

Absolute and relative refractory periods and the sensory conduction velocity of the median and ulnar nerves were determined in six patients suffering from hypokalemia of various origins. Nerve impulse conduction and the absolute refractory period remained normal, but the relative refractory period was shortened to 1.7 to 2.6 ms at serum K+ levels from 1.6 to 2.9 mval/l. As compared with normal values this decrease was statistically significant.

Visual pattern evoked responses and blink reflexes in assessment of MS diagnosis. A clinical study of 135 multiple sclerosis/pathol.

VEPs were measured after pattern reversal in 135 MS patients and 30 control subjects. Neurological findings were documented in a standard manner. An extensive ophthalmological examination of all subjects was part of the study. The latency of P2 was abnormally delayed in 82% of the "definite", in 60% of the "probable" and in 65% of the "possible" MS groups respectively. The VEP was more often delayed in relation to ophthalmological disturbances. Changes in the MS classification had to be made in more than 10% of the patients, due to delay of VEP latency. These were patients with a "spinal" form of MS, which is known to create diagnostic problems. Optically and electrically evoked blink reflexes were recorded in 107 MS patients. All patients with mesencephalic lesions had delayed responses of the optically evoked reflex. 74% of the patients with caudal brainstem lesions had delayed latencies of the components of the electrically evoked blink reflex. The blink reflex was delayed in 18 additional patients without brainstem signs. The possibility of delineating clinically silent brainstem lesions by investigating blink reflexes is discussed.

Cerebrospinal fluid hypoxanthine, xanthine and uric acid levels may reflect glutamate-mediated excitotoxicity in different neurological diseases.

Glutamate-mediated excitotoxicity is associated with adenosine triphosphate (ATP) degradation and generation of oxygen radicals. Hypoxanthine and lactate depict energetic impairment, while xanthine and uric acid reflect activity of radical producing xanthine oxidase. Cerebrospinal fluid (CSF) glutamate, hypoxanthine, lactate, xanthine, and uric acid were investigated in neurological patients. In multiple sclerosis, myelopathy, stroke, epilepsy and viral meningitis glutamate, hypoxanthine, xanthine, and uric acid are increased 2-3-fold compared to controls. Lactate is only elevated in meningitis. Normal lactate dehydrogenase (LDH) levels and absent correlation between the albumin ratio and neurochemical parameters exclude an artificial increase due to cell lysis and barrier damage. Absent correlation between neurochemical parameters within each patient group is most likely related to preserved glial and neuronal uptake mechanisms. CSF hypoxanthine, xanthine, and uric acid levels appear superior to lactate in reflecting glutamate-mediated excitotoxicity in neurological patients.

[Shape changes in contrast VEP in multiple sclerosis: relation to the type of lesion]. / Formveränderungen des Kontrast-VEP bei multipler Sklerose: Beziehung zum Läsionstyp.

VEP changes in MS patients are due to the demyelinating process which causes conduction alterations as well as inhibitory mechanisms. The pattern-shift VEP can show a delay of the main positivity, a diminished amplitude or/and an altered shape and duration. Concerning to series from the literature and own observations on more than 500 MS patients 4 different types of VEP alterations can be observed: 1. NPN complex with P2 delay; 2. broadening with loss of N2 and P2 delay; 3. bifid P2, P100-P135 complex; 4. deformation and dissociation with loss of P2, N105 dominance and amplitude reduction.

Habituation of the blink reflex: computer assisted quantitative analysis.

The electrically evoked blink reflex (BR) was elicited in 20 healthy volunteers, varying the stimulus interval by a computer JN 110. Latencies, amplitudes, reflex duration and reflex areas of early and late components of the BR were analysed by a computer program testing the signal-to-noise ratio, the response configuration and frequency distribution. Changes in habituation related to the stimulus interval can be illustrated best by the progressive diminution of R2 areas. Computing the habituation in relation to the stimulation frequency by a standardized program seems to be a quantitative method to assess habituation in various diseases and during treatment studies.

[Pattern-reversal visual evoked potentials and electroretinography in the early diagnosis of chronic simple glaucoma]. / VEP und Elektroretinographie durch Musterumkehrreizung in der Frühdiagnostik des Glaucoma chronicum simplex.

For differential, therapeutic, and prognostic reasons the recognition of early lesions in glaucoma chronicum simplex is very important. Besides sophisticated ophthalmological investigations optic nerve and retinal functions can be tested by flash and pattern-reversal evoked visual potentials and electroretinograms. 38 glaucomatous eyes were investigated by VEP and ERG applying single and flicker flashes as well as transient pattern-reversal stimuli of different check sizes. The results related to the degree of visual field disturbances show the damage of retinal and neuronal elements in a descending order affecting first of all the macular cones, then the rod system, and later on the elements of the second retinal neuron. The ganglion cells seems to be affected after all.

[Optic nerve involvement in neuro-syphilis: diagnostic evaluation by pattern-reversal visual evoked potentials (VEP) (author's transl)]. / Optikusaffektion bei Neurolues--Diagnose durch das visuell evozierte Potential (VEP).

Pattern-reversal visual evoked potentials (VEP) were recorded in 41 patients suffering from syphilis in different stages. --In a latent syphilis 3 from 50 eyes (6%) had abnormal VEPs although ophthalmological findings were normal. --In neuro-syphilis, however, 16 from 32 eyes (50%) showed delayed responses. Ophthalmological findings were much less abnormal: visual acuity in 12%, visual field in 19%, and either or both of them in 25%. Pupillary disturbances were observed in 62%.

Early auditory evoked potentials: developmental aspects and validity in neuropaediatric and audiologic disorders.

Auditory evoked potentials and in this context especially five waves in the first 10 ms (early auditory evoked potentials = EAEP) are a diagnostic aid in topodiagnosis of posterior fossa diseases. This is due to waves I to V which arise along the acoustic nerve and in brain stem structures such as medulla, pons and mid-brain. Besides an indication about the site of a lesion in the posterior fossa, wave V allows an objective threshold determination. The present results were gained in normal children aged 1-3 years and in children with neuropaediatric and audiologic disorders.

[Arachnoid cyst and tension headache: symptom or accidental finding?]. / Arachnoidalzyste und Spannungskopfschmerz Symptom oder Zufallsbefund?

We report a 34 year old male patient presenting with occipital headache and bilateral shoulder and neck pain. Cranial MRT discloses a large arachnoid cyst ventral to the medulla oblongata. The cyst displaces the caudal medulla oblongata dorsally to an angle of almost 90 degrees without causing myelopathy. Physical examination reveals normal neurological findings without any sign of brainstem lesions or lesions of the medulla oblongata. Orthopedic evaluation shows mild functional abnormalities as expected in tension headache. Multiple electrophysiologic investigations such as motor-, somatosensory-, and acoustic-evoked potentials, masseter and brain stem reflexes, and electromyography of the left M. trapezius were performed and reveal normal results. MR-angiography discloses displacement of the left vertebral artery to the right without stenosis.We discuss the possibility of a causal connection between the cystic lesion and the reported symptoms. Considering the findings based on a review of the available literature we conclude that the pain syndrome is very likely unrelated to the arachnoid cyst. The latter is herewith an accidental finding in a patient with tension headache, and underlines the importance of thoroughfull clinical examination to avoid unnecessary diagnostic or therapeutic procedures.

[The dependence of phase inversion of the visual evoked potential during half-field stimulation on the stimulation target and the pattern size]. / Abhängigkeit der Phaseninversion des VEP bei Halbfeldreizung von Reizort und Mustergrösse.

In 10 young and healthy subjects visual evoked potentials were recorded to monocular whole-field and half-field (12 degrees radius) stimulation, with and without central (3 degrees radius) and peripheral occlusion of the target. The records were made from a horizontal array of 3 occipital electrodes, one placed in the midline 5 cm above the inion and the others 8 cm each lateral of the inion. The early and main components of the VEPs were analyzed and compared. We found that the N2-Peak has its origin in the macular parts of the retina and the P2-peak in the central and peripheral parts of the visual field. Inverted polarity of the P2-peaks contralateral to the stimulated half-field could be observed only when the VEP was recorded with small checks. When using large checks, only the early components inverted. The probable origin of the inverted main components is discussed, being either a simple inverted P2-peak because of the direction of the cortical dipoles, or a new, paramacular N105-peak.

Auditory brain stem responses in patients with human immunotropic virus infection of different stages.

Thirty patients (26 men, 4 women) with human immunotropic virus infection of different stages were examined. Eleven patients had a history of i.v. drug abuse, nine patients had a history of treated lues infection, and one patient suffered from Kaposi's sarcoma. At the time of the examination, opportunistic infections or acute encephalitis were not apparent in any patient. All patients underwent otoneurological examinations, including pure-tone audiometry, caloric vestibular testing, and recording of the auditory brain stem responses (ABR). Six patients reported onset of hearing impairment during the last 3 yr. Two of them had flat sensorineural hearing loss; in the other cases, pure-tone audiometry showed high tone hearing loss with negative recruitment. ABRs were normal in 19 cases, with the latencies for waves III and V and for the I-V interpeak latency significantly delayed when compared to the values of the control group. The frequency of abnormal ABR findings did not correlate to the stage of the disease. The results of the study indicate that auditory and, more specifically, ABR abnormalities commonly occur in human immunotropic virus disease. More studies are necessary to prove whether the ABR is suitable to monitor therapeutic effects.

Hemifacial spasm: location of the lesion by electrophysiological means.

In hemifacial spasm a late abnormal motor response was elicited by the antidromic volley after stimulating a peripheral branch of the facial nerve. The site of the lesion was calculated from the latency of that motor response and the conduction velocity. In 5 patients the distance was long, and corresponded with a tumor or a vascular anomaly at the cerebellopontine region in 3 of them. An artery sling entering the internal acoustic meatus was found in 2 out of 3 patients with short distances. It is concluded that hemifacial spasm results from a nerve lesion that may be located as far peripherally as the internal acoustic meatus. The theory of facial nuclear irritation is incompatible with such a peripheral lesion.

[Normalization of VEP in multiple sclerosis? Course observation in 50 of 500 MS patients]. / "Normalisierung" des VEP bei Multipler Sklerose? Verlaufsbeobachtung bei 50 von 500 MS-Patienten.

Serial recordings of pattern-reversal VEPs have been performed in 50 of 500 MS patients in 4 or more occasions within the last 5 years. 49/96 eyes initially displayed a normal and 47/96 a prolonged P2 latency. A further delay was observed in 9 eyes, while in another 9 eyes the latency improved entering the normal range but in 4 eyes. In two eyes, only, shape and peak configuration normalized too. These results demonstrate the rarity of true normalisation of the contrast VEP after optical neuritis in MS.