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Biomedical subjects

M Keidel

Publications and source records attributed to M Keidel.

At least 19 recordsLinked to original sources
PubMed2000

Inverse covariation of spectral density and correlation dimension in cyclic EEG dynamics of the human brain.

The responsiveness or excitability of the central nervous system (CNS) to external or internal stimuli is systematically altered corresponding to transient changes of the EEG background activity, mainly in the alpha range. We hypothesise that a transient alpha power increase is due to an underlying increase in synchronisation or coupling strength between various neuronal elements or cortical networks. Consequently, the 'network' of the CNS may be more ordered and, hence, less complex in the case of high spectral density, and vice versa. The goals of the present paper are (1) to prove the inverse covariation between spectral density and correlation dimension for a set of human EEG data, (2) to falsify the null hypothesis that the observed relationship is a random one, and (3) to propose a neuronal approach which may explain the observed correlations. A sliding computation of the spectral density and correlation dimension [Grassberger P, Procaccia I (1983) Physica D 9:189-208] of mid-occipital EEG recordings derived from eight awake subjects with eyes closed was performed. The similarity between the two time courses was quantified by similarity measures and descriptive correlation coefficients. The temporal pattern of dimensional complexity showed an inverse relationship with simultaneously computed spectral power changes most pronounced in the alpha range. The group means of similarity measures and correlation coefficients were compared with the corresponding means of a sample set established by 20 Gaussian random signals. Statistically significant differences were obtained at the 0.1% level, rejecting the null hypothesis that the observed relationship is a random one. The results support the idea that the dynamics of the EEG signals investigated reflect a chaotic deterministic process with state transitions from 'high-dimensional' to 'low-dimensional' non-linear dynamics, and vice versa. Adequate neuronal models and approaches to interpret the disclosed transients and the inverse covariation between spectral density and dimensional complexity are proposed, giving additional insight into the integrative functioning of the CNS with respect to the strategy of information processing.

Brain↗
PubMed2000

Malignant pheochromocytoma with progressive paraparesis in von Hippel-Lindau disease.

Pheochromocytomas are a feature of the von Hippel-Lindau disease spectrum, a multisystem disorder of autosomal dominant inheritance. Pheochromocytomas are, however, observed during life with a lower frequency than other features of this disease, such as retinal angiomas, haemangioblastomas of the CNS, and renal carcinomas. We present the highly unusual case of a patient who required an emergency operation for an intradural extramedullary thoracic tumour which was clinically suggestive initially of neurinoma. We present evidence from NMR, histological and isotope scan investigations of this being a pheochromocytoma metastasis and of an additional right-sided paraganglioma at the same height. A detailed history revealed that this patient had suffered from four other pheochromocytomas and two other paragangliomas, in addition to retinal angiomatosis of von Hippel-Lindau disease. This case is extraordinary due to (i) the unusual site of the metastasis, (ii) the neurological requirement for an emergency operation of pheochromocytoma, (iii) metastasis of pheochromocytoma in von Hippel-Lindau disease (only eight previous cases), and (iv) the number of recurrent pheochromocytomas. It clearly demonstrates the necessity for frequent and life-long follow-up in von Hippel-Lindau disease.

Adrenal Gland Neoplasms↗
PubMed1998

[Pain quantification after whiplash trauma using computer-interactive pressure-pain measurement].

In patients with an acute cervicocephalic pain syndrome following whiplash injury (n = 12), pressure-pain scores for the splenius and the trapezius muscles on both sides, for the fingers on both sides and for the skull were recorded and compared to a control group. A computer-aided pain measurement was applied, which is presented as an improvement of pressure algesimetry. During constant application of pressure stimuli, the patient rated the increasing pain on a visual analogue scale, resulting in a curve of pain intensity against time. Slope and integral of the curve proved to be the most reliable parameters. After whiplash injury, significantly increased pain scores were found for the splenius muscle on both sides, for the left trapezius muscle and for the left finger whereas there was only a tendency of increased pain at the other stimulation sites. The presented method allows quantification of the cervical syndrome with neck and shoulder muscle sprain caused by whiplash injury. This objective and rater-independent method is of great value for diagnostic, therapeutic and medico-legal purposes in the assessment of the disease course and in clinical therapy trials.

Adolescent↗
PubMed1998

Myopathy in two siblings with nephropathic cystinosis.

Nephropathic cystinosis is a hereditary disorder characterized by a specific defect in the transport of cystine across the lysosomal membrane, leading to an accumulation of protein-free cystine in tissues, including conjunctiva, liver, bone marrow and kidney. Renal transplantation is necessary because of renal failure. With improved life-expectancy, neurological complications have been reported, including cases of distal myopathy diagnosed ante- and post-mortem. We report on two further rare cases of two siblings suffering from cystinosis who developed a predominantly distal myopathy, proven electrophysiologically and on biopsy during life. The reported clinical picture of a distal atrophy resembling a neurogenic disease, confirms a picture apparently typical in cystinosis. Possible effects of cysteamine therapy on the course of the myopathy are discussed. Copyright 1998 Lippincott Williams & Wilkins

Journal Article↗
PubMed1997

[Post-traumatic headache].

Head trauma (HT) and whiplash injury (WI) is followed by a posttraumatic headache (PH) in approx. 90% of patients. The PH due to common WI is located occipitally (67%), is of dull-pressing or dragging character (77%) and lasts on average 3 weeks. Tension headache is the most frequent type of PH (85%). Besides posttraumatic cervicogenic headache or symptomatic, secondary headache due to SDH, SAB, ICB or increased ICP, migraine- or cluster-like headache can be observed in rare cases. Prolonged application of analgetics (> 4 weeks) can cause a drug induced headache. In 80% of patients PH following HT shows remission within 6 months. Chronic PH lasting at least 4 years occurs in 20%. Unfavorouble prognostic factors include an age higher than 40 yrs, a low intellectual, educational and socio-economic level, previous HT or a history of alcohol abuse. A prolonged PH due to WI can be expected in patients with initially severe headache, with an extensive decrease of mobility of the cervical spine, with subjective impediment, with depressive mood, with somatic-vegetative complaints, with a history of pretraumatic headache and with increased age. Acute PH is treated with analgesics, antiphlogistics and/or muscle relaxants; chronic PH with thymoleptics (e.g. Amitryptiline or Amitryptiline oxide). Additional physical therapy (e.g. wearing a cervical collar for a short time, hydrocollator pack), physiotherapy incl. muscle relaxation techniques (Jacobson) and psychotherapy can be performed. Medico-legal issues should be solved as soon as possible.

Analgesics↗
PubMed1997

Headache and the cervical spine: a critical review.

Headache related to the cervical spine is often misdiagnosed and treated inadequately because of confusing and varying terminology. Primary headaches such as tension-type headache and migraine are incorrectly categorized as "cervicogenic" merely because of their occipital localization. Cervicogenic headache as described by Sjaastad presents as a unilateral headache of fluctuating intensity increased by movement of the head and typically radiates from occipital to frontal regions. Definition, pathophysiology; differential diagnoses and therapy of cervicogenic headache are demonstrated. Ipsilateral blockades of the C2 root and/or greater occipital nerve allow a differentiation between cervicogenic headache and primary headache syndromes such as migraine or tension-type headache. Neither pharmacological nor surgical or chiropractic procedures lead to a significant improvement or remission of cervicogenic headache. Pains of various anatomical regions possibly join into a common anatomical pathway, then present as cervicogenic headache, which should therefore be understood as a homogeneous but also unspecific pattern of reaction.

Combined Modality Therapy↗
PubMed1996

[Headache and the cervical spine. A critical review].

Headache in association with the cervical spine is often misdiagnosed and treated inadequately due to confusing and varying terminology. Primary headaches such as tension-type headache and migraine are incorrectly categorized as "cervicogenic" merely because of their occipital localization. Cervicogenic headache described by Sjastaad presents as a unilateral headache of fluctuating intensity increased by movement of the head and typically radiating from occipital to frontal regions. Definition, pathophysiology, differential diagnosis and therapy of cervicogenic headache shall be demonstrated. Ipsilateral blockades of the C2/ C3 root and/or the major occipital nerve allow a differentiation between migraine and other primary headache syndromes. Neither pharmacological nor surgical or chiropractic procedures lead to an improvement or remission of cervicogenic headache. Pain of various anatomical regions possibly join into a common anatomical pathway then presenting as cervicogenic headache, which should therefore be understood as a homogeneous but also unspecific pattern of reaction.

Cervical Vertebrae↗
PubMed1994

[Pathological jaw opening reflex after whiplash injury].

The brainstem mediated inhibitory reflex of the m. temporalis was investigated on average 3 days after the accident in 61 patients (f = 36; m = 25; mean age = 28 years +/- 9 SD) who presented an acute cervico-cephalic syndrome with posttraumatic headache and neck pain following acute whiplash injury but without neurological deficits, bone injury of the cervical spine or combined direct head trauma. We postulated a disturbed reflexive temporalis muscle inhibition in patients with 'whiplash cephalalgia', as has previously been reported for classical muscle tension headache. Latencies and durations of the early and late exteroceptive EMG suppression (ES1 and ES2) and the interposed EMG activity (IE) of the voluntarily contracted right temporalis muscle following ipsilateral stimulation of V/2 + 3 afferents were recorded. The reflex data were compared to a cohort of 69 age and sex matched normal subjects (f = 37; m = 32; mean age = 28 years +/- 7 SD). The following significant reflex changes were found in patients: a shortened duration of ES2 with delayed onset and premature ending, a slight prolongation of ES1 and IE, a delayed onset of IE and a diminished ratio of ES2:ES1 and ES2:IE. We conclude that the abnormality of the antinociceptive reflex is based on a transient dysfunction of the brainstem mediated reflex circuit following the acceleration trauma, which can be considered a neurophysiological correlate of the posttraumatic cervico-cephalic pain syndrome and may be useful as a 'biological marker' in monitoring the time course of recovery from pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

[Cerebral angiitis or central side effects after lumbar myelography (with intracerebral vascular spasm)].

This is a case report of severe neurological complications following lumbar radiculography with the non-ionic x-ray contrast agent Iopamidol. The complication, which consisted of serious mnestic disturbances and various neurological deficits including hemiparesis, was due to intracerebral vascular spasms, demonstrated by cerebral angiography, and TCD followed by multiple cerebral infarctions, demonstrated by MRI. A possible causal relationship between the cerebral vascular spasm and intrathecal administration of Iopamidol is discussed.

Cerebral Angiography↗
PubMed1993

["Paralysis cruciata"--a rare brain stem lesion syndrome after cervical vertebrae trauma].

Bell's cruciate paralysis with severe paresis or paralysis of the upper extremities and no or minimal paresis of the lower extremities represents a rare lesion of the pyramidal decussation of the lower brain-stem. MRI may show a hypointense lesion on T1-weighted imaging. Prognosis in this syndrome is dependent on the extent of involvement of surrounding brain-stem-structures, as described in three different cases.

Adult↗
PubMed1992

[Prospective follow-up of neuropsychological deficits after cervicocephalic acceleration trauma].

30 patients with acute cervico-cephalic syndrome following whiplash injury (neck and head pain, vegetative symptoms and subjective complaints of impaired mental functions) without neurological deficits were investigated in a prospective follow-up of 3 months with neuropsychological examination in the acute phase (x = 5.7 days) and again 6 and 12 weeks after the accident. Attention, concentration, cognition and verbal and visual memory functions were quantified by neuropsychological tests, and changes over the observation period were analysed. In the acute phase all neuropsychological functions were below the individual's normal level. Deficits in attention and concentration recovered within the first 6 weeks. Further recovery within the following 6 weeks were observed in visual memory, imagination and analytic capacity. The capability of verbal memory and abstraction, cognitive selectivity and information processing speed was impaired for a longer time and first recovered after 12 weeks. In conclusion, intraindividual neuropsychological deficits following whiplash injury can be quantified and monitored to show the time course of recovery. Thus in clinical and forensic practice the diagnosis of a pseudoneurasthenic or even "neurotic" syndrome in acute whiplash injury should be made with caution.

Accidents, Traffic↗
PubMed1991

Relationship between electrical and vibratory output of muscle during voluntary contraction and fatigue.

Measurements were done on the biceps muscles of 6 healthy volunteers to record simultaneously the surface electromyogram (EMG) and vibromyogram (VMG) by means of a piezoelectric device (accelerometer). The VMG is generated by mechanical waves due to the contraction mechanism and often measured as sound. The frequency spectrum and integrated value (IEMG and IVMG) of both signals were calculated. Both IEMG and IVMG showed a clear linear correlation with force, although at high forces, the variability of the VMG became rather high. Two series of experiments were performed to study the EMG and VMG changes in relation to changes induced by fatigue: (1) during constant force at 50% of the maximal voluntary contraction (MVC) and recovery; (2) for one 1 minute during declining force at MVC. The main finding was that the IVMG was related to the absolute force, irrespective of the fatigue state of the muscle. In contrast, the IEMG showed the well-known changes during fatigue, such as an increase during endurance. The spectral changes of the two measurements also showed a divergence. The spectra of the EMG shifted to lower frequencies in both fatigue protocols. In contrast, the spectra of the vibratory signal did not shift, except for several measurements at MVC. However, the shape did change to a somewhat flatter spectrum with less pronounced peaks. Possible explanations for this different behavior are discussed. It is concluded that the vibratory energy generated by the contraction mechanism is linearly related to force. Changes induced by fatigue do not alter this relationship: this contrasts with the behavior of the EMG.(ABSTRACT TRUNCATED AT 250 WORDS)

Electromyography↗