Search PubMed⌕ Search

Biomedical subjects

H C Hopf

Publications and source records attributed to H C Hopf.

At least 73 records · Page 4Linked to original sources
PubMed1998

Anticipation in familial cavernous angioma: ascertainment bias or genetic cause.

OBJECTIVES: Anticipation has been linked to unstable trinucleotide repeats in many neurological disorders. We examined the hypothesis of genetic anticipation in familial cavernous angioma (FCA) of the central nervous system. MATERIAL AND METHODS: The mean ASO of affected individuals was compared between successive generations in 55 families. Intergenerational pair-wise comparisons were employed to avoid several ascertainment biases. Regarding severity of disease both type of manifestation and number of cavernous angiomas were compared between generations. RESULTS: The mean ASO decreased significantly both from the first to the second generation (31.6 vs 17.8 years; P = 0.000) and from the second to the third generation (17.8 vs 6.7 years; P = 0.002). The pair-wise comparisons also showed significantly earlier ASO. No clear evidence for anticipation with regard to severity of disease was found. CONCLUSIONS: Molecular genetic studies will determine whether trinucleotide repeats are the underlying mechanism for our observation of anticipation in FCA.

Adolescent↗
PubMed1998

Isolated voluntary facial paresis due to pontine ischemia.

We describe a patient with isolated voluntary facial paresis due to a unilateral lacunar lesion in the contralateral mediodorsal middle base of the pons. Transcranial magnetic stimulation confirmed the involvement of supranuclear corticofacial tract fibers and sparing of the corticolingual and corticospinal connections. This observation demonstrates that the fibers conveying voluntary orofacial activation descend mediodorsally at the level of the middle pons and that the fibers conveying emotional activation may be assumed to converge below this level.

Aged↗
PubMed1997

Nociceptive masseter inhibitory reflexes evoked by laser radiant heat and electrical stimuli.

Electrical stimulation of the mental nerve evokes two suppression periods SP1 and SP2 in masseter muscle activity bilaterally. In order to investigate a possible nociceptive origin of the suppression periods, we compared the reflex responses evoked by electrical stimulation and by selective activation of nociceptors in hairy skin using painful infrared laser stimuli. The SP was elicited during more than 90% maximal voluntary contraction. Thresholds for detection, pain, and SP in the mental nerve area were determined by the method of limits. A suppression period was evoked by laser stimuli in nine of ten subjects bilaterally. The mean onset latency was 46.9 ms, the mean duration 58.9 ms. The electrical threshold of SP1 (9 mA) was 7.7 x I(0), about 20% smaller than I(P), and significantly higher than I(SP2) (4.7 mA). The onset latencies and durations were 11.7 ms and 21 ms for SP1, and 45 ms and 42.7 ms for SP2 (stimulus intensity 2 x I(P)). The mean difference in onset latencies between laser SP and electrically evoked SP1 was 35.1 +/- 6.2 ms, which closely matches the nociceptor response latency to a laser heat pulse. Based on the threshold and the onset latency we conclude that at least SP1 and laser SP are nociceptive in origin and mediated by group III fibers.

Adult↗
PubMed1997

Evaluation of carpal tunnel syndrome in patients with polyneuropathy.

The difference between the median nerve latency to the second lumbrical muscle and the ulnar nerve latency to the second interosseous muscle (L-I DIFF) was tested in a prospective study to discriminate whether prolonged distal motor latency of the median nerve in patients with polyneuropathy (PNP) reflects an additional carpal tunnel syndrome (CTS). We investigated 92 patients (107 hands) with CTS, 30 patients (34 hands) with PNP, 22 patients (27 hands) with CTS and coexisting PNP (PNP + CTS), and 77 controls (87 hands). L-I DIFF was significantly prolonged in both the CTS and PNP + CTS patients as compared to PNP patients and controls. It proved to be the most specific test to differentiate between diffuse (PNP) and focal (entrapment) nerve disorder.

Adult↗
PubMed1997

Pain-evoked blink reflex.

The electrically evoked blink reflex (BR) consists of an ipsilateral R1 component (R1) at 11 ms and two bilateral components R2 at 33 ms and R3 at 83 ms. It is still unclear whether the R2 is mediated by activation of tactile or nociceptive afferents. For testing the nociceptive hypothesis, nociceptors of the supraorbital nerve were selectively activated by infrared laser stimuli in 10 subjects. Only painful laser stimuli evoked a bilateral early polyphasic BR response (LR2) at 71 ms. Stimulation of infraorbital and mental nerve dermatomes was equally effective. A late bilateral reflex response at 130 ms was occasionally observed. Regarding the nociceptor activation time of about 40 ms, onset latencies were within the range of the electrically evoked R2 and R3, respectively. The good accordance of R2 and LR2 may be due to activation of identical nociceptive fibers or to convergence of electrically evoked tactile and laser-elicited nociceptive input onto common multireceptive neurons.

Adult↗
PubMed1997

["Phobic postural vertigo". A further differentiation of psychogenic vertigo conditions seems necessary].

Due to the results of an interdisciplinary study on patients with vertigo as the chief symptom and on the background of psychodynamic theories concerning anxiety disorders the term of phobic postural vertigo (Brandt & Dieterich 1986) is discussed. It becomes obvious that phobic postural vertigo is a generalizing term which encompasses different forms of psychogenic vertigo. The authors plead for a more differentiated diagnosis and subgroup oriented classification of vertigo caused by psychiatric disorders.

Adolescent↗
PubMed1997

A fully automated system for the evaluation of masseter silent periods.

Exteroceptive suppression of masseter muscle activity, 'masseter inhibitory reflex', comprises one or 2 silent periods (SP1 and SP2) interrupting the voluntary activation. The main problem when evaluating exteroceptive suppression is the lack of an objective and precise measure for the onset and end of the silent period which so far has not been overcome by various automated systems. We describe a new fully automated system for determining the onset and end of the masseter silent period. The decision approach is essentially based upon deterministic properties of median filters which are used to partition the local variances of the EMG traces into constant segments and edges between them. The system was tested in 13 healthy volunteers with 2 subjects tested serially 10 times each to get estimates of the inter- and intra-individual variability. The performance of the system compared favourably to that of a simpler approach and to earlier results from our laboratory. The inter-individual variability of the SP1 onset was 17 times smaller than when based on a subjective decision process.

Adolescent↗
PubMed1997

Cortico-bulbar fibers to orofacial muscles: recordings with enoral surface electrodes.

A new recording technique was developed to eliminate current problems on recording transcranial evoked facial muscle responses. A fork-shaped device equipped with 2 pairs of Ag/AgCl-electrodes was inserted enorally at the buccinator muscle level. Advantages offered by this method comprise clearly defined negative deflection of the compound muscle action potential, lack of relevant volume conduction from adjacent muscles, reliability of amplitude criteria, absence of interfering stimulus artifacts, easy achievement of preactivation, and noninvasive recording by surface electrodes. In 43 healthy subjects transcranial magnetic stimulation evoked contralateral responses at a mean latency and mean amplitude of 10.3 +/- 1.1 ms and 1.6 +/- 1.1 mV, respectively on the right side of the face and of 9.9 +/- 1.0 ms and 1.6 +/- 1.1 mV, on the left side of the face. Ipsilateral cortical evoked responses were observed in 29 and 25 subjects (left and right side of the face) at a mean latency and amplitude of 10.7 +/- 2.5 ms and 0.8 +/- 0.5 mV, respectively on the left side of face and of 11.9 +/- 3.2 ms and 1.1 +/- 1.2 mV, on the right side of face. No responses were obtained in 2 and 4 subjects (left and right side of the face), and could not be assessed due to simultaneous facial nerve stimulation in 12 and 14 subjects (left and right side of the face).

Adolescent↗
PubMed1997

Impaired cortico-bulbar tract function in dysarthria due to hemispheric stroke. Functional testing using transcranial magnetic stimulation.

We investigated cortico-lingual and cortico-orofacial tract function utilizing transcranial magnetic stimulation in 18 consecutive patients with dysarthria due to hemispheric stroke. Delayed responses (conduction time > mean + 2.5 SD of that of 43 controls) or absent responses were considered abnormal. In all patients, motor-cortex stimulation of the lesion side demonstrated absent (13 patients) or delayed (five patients) responses to the tongue bilaterally (17 patients) or unilaterally (one patient). In 14 patients the contralateral orofacial responses were either absent (13 patients) or delayed (one patient). According to the electrophysiological findings, all lesions revealed by CT or MRI, were located within the pyramidal tract at the lower motor cortex (n = 4), the corona radiata (n = 7), and the genu of the internal capsule (n = 3) or its posterior limb (n = 4). We conclude that interruption of the cortico-bulbar tract fibres to muscles involved in articulation is a frequent cause of dysarthria in hemispheric stroke.

Aged↗
PubMed1997

Isolated cranial nerve palsies in multiple sclerosis.

During a 10 year period 24 patients with definite multiple sclerosis with isolated cranial nerve palsies were studied (third and fourth nerve: one patient each, sixth nerve: 12 patients, seventh nerve: three patients, eighth nerve: seven patients), in whom cranial nerve palsies were the presenting sign in 14 and the only clinical sign of an exacerbation in 10 patients. MRI was carried out in 20 patients and substantiated corresponding brainstem lesions in seven patients (third nerve: one patient, sixth nerve: four patients, eighth nerve: two patients). Additional abnormal findings of electro-oculography, or masseter reflex, or blink reflex, or combinations of these were found in 20 patients and interpreted in favour of a brainstem lesion at the level of the respective cranial nerve. In 11 of 14 patients with isolated cranial nerve palsies as the presenting sign of multiple sclerosis, dissemination in space was documented by MRI, and in the remaining three by evoked potentials. In patients with multiple sclerosis with isolated cranial nerve palsies, MRI is the most sensitive method of documenting dissemination in space and electrophysiological testing the most sensitive at disclosing brainstem lesions.

Adult↗
PubMed1997

[Illness-specific control issues in patients with vertigo as the main symptom].

The study explored the relationship between health locus of control and anxiety in 90 patients with the chief complaint of dizziness/vertigo. The patients were subjected to a neurological examination, including standardised history, physical examination, electronystagmography with caloric testing and posturography, auditory and visually brainstem-evoked responses, masseter reflex, vertebrobasiliar transcranial Doppler, optional: cranial imaging (CCT/MRI), cardial diagnostic, and a psychiatric-psychodynamic examination (including psychometric tests: STAI-G X2, KKG, SBA-S). The whole group of patients (psychogenic and organic dizziness) had a specific pattern of health locus of control: "double health external" (Type IV-Wallston and Wallston 1982). Patients with psychogenic dizziness showed a higher score of external locus of control (chance) compared with the patients with organic dizziness. High anxiety scores were accompanied by high scores of external locus of control (powerful others and chance) above all in the patients with psychogenic dizziness. Implications for therapy are discussed.

Adolescent↗
PubMed1996

Isometric muscle contractions after double pulse stimulation. comparison of healthy subjects and patients with myotonic dystrophy.

Isometric contractions of the adductor pollicis muscle were studied in healthy subjects and patients with myotonic dystrophy after single and double stimuli of the ulnar nerve using a wide range of interstimulus intervals (ISI, 0.4-180 ms). In healthy subjects, the force contributed by a second stimulus was greater than the single twitch force being maximal (mean + 140%) at 12-ms ISI. In myotonic dystrophy, the force contributed by the second stimulus was (relative to a reduced twitch amplitude) increased (mean + 204%) with a maximum at 4.8-ms ISI. An abnormal increase of force was only recorded if the single twitch force was clearly reduced. The absolute refractory period of muscle contraction (normal range 1.2-1.6 ms, mean 1.35 ms) was shortened in all patients (mean 1.01 ms) except one (1.2 ms). The ISI showing the maximal force were related to those showing the maximal prolongation of the contraction time in healthy subjects (r = 0.71) but not in patients. The rate of force development contributed by a second stimulus was slower than expected from the summation of two single twitches with short stimulus intervals (3-40 ms) a phenomenon called early depression. In patients, the early depression was reduced or abolished within this range of ISI as has been found in dystrophic mouse muscles. The optimal ISI in patients was shifted towards very short times and together with the other disturbances it is suggested that activation of diseased muscle by motoneurons may be less effective, being an additional factor leading to weakness in myotonic dystrophy.

Adult↗
PubMed1996

Electrophysiological brainstem investigations in obstructive sleep apnoea syndrome.

Phasic inspiratory genioglossus activity prevents pharyngeal airway collapse in healthy subjects during sleep and is diminished or absent in obstructive sleep apnoea syndrome (OSAS), thus leading to pharyngeal obstruction. Case reports of OSAS after pontomedullary lesions indicate that impaired inspiratory genioglossal activity may result from brainstem lesions. We therefore investigated brainstem functions in 18 awake patients with OSAS using brainstem auditory evoked potentials, blink reflex, masseter reflex, masseter inhibitory reflex (in 11 of 18 patients), magnetic evoked potentials of the tongue and electrooculography with vestibular testing. Fifteen of 18 patients showed no electrophysiological abnormalities. One patient had a left pontine and two patients a bilateral pontomesencephalic lesion, although a causal connection with OSAS was not conclusively confirmed. Our results do not support the assumption of a relevant structural brainstem lesion in OSAS patients with normal neurological findings.

Adult↗
PubMed1996

The R3 component of the blink reflex: normative data and application in spinal lesions.

The clinical value of the R3 component (R3) of the blink reflex (BR) for differentiating between lesions at the medulla oblongata and cervical spinal cord level is still unclear. In 50 healthy volunteers (25 women, 25 men, aged 20-75 years) reproducible ipsi- and contralateral R3 responses could be evoked showing a mean onset latency of 84 ms, a duration of 32 ms and a side-to-side difference of almost 3 ms. The latency increased with age. Eleven patients with lesions of the cervical spinal cord (segments C1-C6) showed normal R3 latencies. In 4 patients with pathology of the brain-stem, however, R3 was abnormal, showing identical changes as observed with the R2 component. Our results suggest that the reflex arc of R3 does not descend to the cervical spinal cord but within the brain-stem possibly takes the same connections as the R2 component.

Adult↗
PubMed1996

[Vertigo and anxiety disorders--results of interdisciplinary evaluation].

BACKGROUND: Vertigo is a common symptom that often remains unexplained despite extensive medical evaluation. Psychiatric and psychosomatic disorders are usually considered after all somatic causes of vertigo have been ruled out. METHODS: Eighty-three patients referred to neurological or psychosomatic outpatient treatment received an extensive neurootologic and psychosomatic evaluation: one (or two) diagnostic psychiatric psychodynamic exploration(s), a structured interview, psychometric tests (SCL-90-R, STAI-G X2 and GBB). The patients were divided into four diagnostic groups: psychic causes only (psychogenic group), neurootologic causes only (somatic group), both diagnoses (psychosomatic group), neither diagnosis (group IV). RESULTS: Twenty-three patients had organic vertigo, thirty-nine patients had psychogenic vertigo and in seventeen cases a vestibular lesion initiated the development of a neurotic disorder, particular anxiety disorder. Most of the patients of the psychogenic and psychosomatic group had anxiety or phobic disorders. The patients with psychogenic or psychosomatic symptoms of vertigo generally report a higher level of subjective distress; the periods of disability are significant longer. CONCLUSIONS: The study suggests that assessment of psychiatric and psychosomatic symptoms should always accompany, not follow, neurootologic evaluation of vertigo. An early interdisciplinary therapy should be started to prevent the chronicity of the symptomatology.

Adult↗