Biomedical subjects

Mark Kushnir

Publications and source records attributed to Mark Kushnir.

6 recordsLinked to original sources

PubMed2005

Pharmacokinetics of a testosterone gel in healthy postmenopausal women.

BACKGROUND: The paucity of pharmacokinetic data on androgen formulations in women has hindered clinical trials of testosterone supplementation in women. OBJECTIVE: The objective of this study was to determine the time course and profile of serum testosterone concentrations during treatment with different doses of testosterone gel in postmenopausal women and assess whether estrogen treatment affects the pharmacokinetics of testosterone gel. METHODS: Postmenopausal women with total testosterone levels less than 33 ng/dl after baseline 24-h sampling were treated with 4.4, 8.8, or 13.2 mg testosterone gel daily for 7 d each in random order, with a 7-d washout period between doses. We studied 13 women who had not received estrogen therapy (group I) and 13 who had received stable estrogen therapy for 3 months or more (group II). Total and free testosterone concentrations were measured for 48 h on the seventh day of each dose administration. RESULTS: Twenty-six women were randomized; of these, 24 were evaluable, 13 in group I and 11 in group II. The average steady-state concentrations (Cav) of serum total and free testosterone increased with increasing testosterone dose and were highly correlated with the dose (dose effect, P < 0.00001), but were not affected by estrogen therapy (P = 0.43). In both groups, the 4.4-mg dose increased Cav total and free testosterone into the mid- to high-normal range, whereas 8.8- and 13.2-mg doses raised total (Cav: 22.3, 51.6, 80.3, and 92.0 ng/dl in group I; 22.7, 59.8, 82.0, and 114.3 ng/dl in group II at 0, 4.4, 8.8, and 13. 2 mg, respectively) and free testosterone (5.9, 8.4, 11.5,12.8 pg/ml in group I and 5.0,7.6,11.1,10.8 in group II, respectively, at the various doses) above the physiological range. The area under the curve, maximum and minimum concentrations, and the change in Cav for total and free testosterone were dose related and significantly higher during administration of the 13.2-mg dose than during the 0- or 4.4-mg dose; estrogen therapy had no significant effect on these measures. Serum estradiol, LH, FSH, and SHBG levels did not change significantly at any dose. Testosterone gel was well tolerated. CONCLUSIONS: Administration of testosterone gel to postmenopausal women raised total and free testosterone concentrations in proportion to the administered dose without affecting estradiol levels. A 4.4-mg dose raised testosterone levels into the mid- to high-normal range. Previous estrogen therapy had no significant effect on testosterone pharmacokinetics over this short duration.

Administration, Topical↗

PubMed2005

Medial dorsal superficial peroneal nerve studies in patients with polyneuropathy and normal sural responses.

We studied medial dorsal superficial peroneal (MDSP) nerves in 52 patients with clinical evidence of mild chronic sensorimotor polyneuropathy and normal sural nerve responses, in order to assess the diagnostic sensitivity and usefulness of MDSP nerve testing in electrodiagnostic practice. To determine the effect of age on MDSP nerve parameters, 98 normal subjects were also examined. Electrodiagnostic evaluation involved studies of motor nerve conduction in tibial, peroneal, and median nerves; sensory nerve conduction in sural, MDSP, median, and radial nerves; tibial and peroneal nerve F waves; H reflexes from the soleus muscles; and needle electromyography of gastrocnemius and abductor hallucis muscles. Among the patients, 49% had low-amplitude sensory responses in MDSP nerves and 57% had either slowing of sensory conduction velocity or no sensory responses on proximal stimulation. MDSP nerve amplitude, tibial nerve motor velocity, and H reflexes were the most sensitive for detection of mild chronic symmetrical axonal sensorimotor polyneuropathy. MDSP nerve testing should be included in the routine electrodiagnostic evaluation of patients with suspected polyneuropathy and normal sural nerve responses.

Action Potentials↗

PubMed2005

Approach to benign paroxysmal positional vertigo in old age.

BACKGROUND: Benign paroxysmal positional vertigo is a common and treatable vestibular disorder characterized by attacks of positional vertigo. Although elderly patients often complain about unsteadiness, the symptom of positional vertigo is seldom reported. Several studies on BPPV in the elderly reveal a low success rate in the treatment of this entity. OBJECTIVES: To assess the clinical characteristics and treatment outcome of BPPV in elderly patients and to compare them with those of the general population treated at our dizziness clinic. METHODS: We reviewed the medical records of 23 patients above age 75 who were treated at our dizziness clinic for BPPV during the years 1998-2004. Their clinical data, BPPV characteristics and treatment outcome were compared with the data of 30 consecutive BPPV patients who represented the general population. RESULTS: No differences in gender distribution, duration of BPPV, treatment responsiveness or recurrence rate were found between elderly patients as compared to the general population. The duration of the last attack of positional vertigo was found to be longer in the elderly, probably due to the delay in recognition of symptoms and accessibility of a dizziness clinic. CONCLUSIONS: Our study shows that BPPV characteristics and treatment effectiveness, as measured by negative Dix-Hallpike maneuver, are not age-dependent and there is no need for a special approach or cautiousness in prognosis prediction. It is important to search actively for this condition since treatment leads to amelioration of unsteadiness and improved well-being in these patients.

Adult↗

PubMed2003

Phobic postural vertigo: a new proposed entity.

BACKGROUND: Dizziness and vertigo can be a complaint in various psychiatric conditions where it usually constitutes only one of the features of the syndrome. Lately, a somatoform disorder characterized by almost mono-symptomatic dizziness and unsteadiness has been described. Since phobic postural vertigo usually presents without anxiety or other psychological symptomatology, patients with this condition seek help at neurologic and otolaryngologic clinics where they are often misdiagnosed as suffering from organic vertigo. OBJECTIVES: To present the clinical features of 55 consecutive patients diagnosed with phobic postural vertigo at our clinic during 1998-2002. METHODS: We conducted a retrospective review of patients' medical records and report two typical cases for illustration. RESULTS: The patients presented with complaints of unsteadiness with or without dizziness, and attacks of sudden veering that caused them to grasp for support. Accompanying anxiety was admitted by only 5% and vegetative symptoms were reported in 18%. In 16% the symptoms resulted in avoidance behavior. A stressful life event or an unrelated somatic disease triggered the onset of PPV in 35% of patients, whereas a vestibular insult preceded the symptoms in 13%. The mean duration of symptoms was 26.7 +/- 39.1 months (range 0.5-20 years). In 72% of patients the symptoms resolved after the psychological mechanism of their symptoms was explained to them; 24% improved with antidepressant treatment (selective serotonin reuptake inhibitors or tricyclic antidepressants), and only in 4% did the symptoms persist. CONCLUSIONS: Since PPV is a frequently encountered diagnosis at some specialized dizziness clinics, familiarity with this entity resulting in early diagnosis can avoid unnecessary examinations and lead to effective treatment.

Adolescent↗

PubMed2002

H reflex threshold in Parkinson's disease patients for different stimulus duration.

Electrical stimulus, with duration starting at 0.1 ms and gradually increased to 1.0 ms, was used for eliciting the H reflex in 14 normal subjects and 19 patients with Parkinson's disease (PD). In 71.1% of normal subjects and in 13.2% of PD patients the H reflex to M response threshold ratio (H/M TR) was <1 and the H reflex was obtained before the M response for all duration stimuli. For all stimulus durations a significant difference between the H/M TR in normal subjects and PD patients was found (t test 0.002-0.007). The duration effect was found to be highly significant-H/M TR for short stimulus duration was greater than for long stimulus durations (p<0.001). The optimal stimulus duration for evaluating H reflex behavior in PD patient was 0.2 ms. These very significant differences in behavior of the H reflex in PD patients could be used as another parameter in the assessment of extrapyramidal rigidity in PD patients.

Adult↗

PubMedDate not supplied

Approach to bilateral benign paroxysmal positioning vertigo.

BACKGROUND: Bilateral benign paroxysmal positioning vertigo (bBPPV) is rather rare, accounting for up to 10% in the reported benign paroxysmal positioning vertigo (BPPV) series. Inappropriate head positioning during testing in unilateral BPPV causes the otolith debris in the uppermost ear to move toward the cupula, resulting in an inhibitory nystagmus and mimicking bBPPV. PURPOSE: We analyzed the clinical data of patients with bilaterally positive Dix-Hallpike maneuver and compared them with the characteristics of patients with unilateral BPPV. We further tried to propose a simple schematic approach to the treatment of patients with bilaterally positive Dix-Hallpike maneuver. MATERIALS AND METHODS: Medical records of 232 patients treated for BPPV at our dizziness clinic during 1999 to 2003 were reviewed. An algorithm used for the treatment of patients with bilaterally positive BPPV is discussed. RESULTS: Twenty-eight patients with bilaterally positive Dix-Hallpike test were found. Sixteen were diagnosed with bBPPV, and 12 were diagnosed with unilateral mimicking bBPPV. Thirty patients with unilateral posterior canal BPPV served as control subjects. No difference in age, sex distribution, duration of symptoms, number of treatments per ear, and recurrence was found between bBPPV and unilateral BPPV. The female sex appeared to be predisposed for more treatments. The total duration of BPPV symptoms obtained by history was found to correlate with the number of recurrences after treatment. CONCLUSIONS: We conclude that bBPPV can be readily distinguished from unilateral mimicking bBPPV. Patients with bBPPV do not differ from patients with unilateral BPPV in clinical characteristics. The mechanism of otolith debris dislodgment appears to be the main cause of bilaterality, trauma being a more common trigger than other known causes of BPPV.

Adult↗