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Biomedical subjects

C Yiannikas

Publications and source records attributed to C Yiannikas.

At least 19 recordsLinked to original sources
PubMed2006

Utility of magnetic resonance imaging in diagnosing ulnar neuropathy at the elbow.

OBJECTIVE: Magnetic resonance imaging (MRI) of the ulnar nerve is being increasingly employed in the diagnosis of ulnar neuropathy at the elbow (UNE). Our aims were to: (i) assess the sensitivity of MRI in diagnosing UNE, especially in cases where neurophysiologic studies were non-localizing, (ii) determine the spectrum of MRI abnormalities in patients presenting with symptoms and signs of ulnar neuropathy, (iii) assess whether MRI findings differ between grades of UNE severity, and (iv) to see if MRI findings give an input into the pathological mechanisms of UNE. METHODS: Clinical, neurophysiologic, and radiologic (MRI) records were reviewed in 52 patients with symptoms and signs of ulnar neuropathy. Ulnar nerve MRI studies were assessed by an unblinded observer. RESULTS: The sensitivity of MRI at diagnosing UNE was higher than conventional nerve conduction studies, 90 versus 65%, respectively. In patients with non-localizing neurophysiologic studies (n=19), MRI disclosed changes consistent with UNE in 16 (84%) cases. The most frequent MRI findings included a combination of high signal intensity and nerve enlargement (63%), followed by nerve compression (27%) and isolated high signal intensity (23%), and isolated nerve enlargement (2%). There was no significant difference between patients with localizing and non-localizing neurophysiologic testing. Lastly, there were no differences between different grades of UNE, suggesting that UNE may be a neurophysiologically heterogeneous disorder. CONCLUSIONS: MRI studies proved to be more sensitive than conventional nerve conduction studies at diagnosing UNE. In addition, the MRI studies were highly sensitive in patients with non-localizing UNE. SIGNIFICANCE: Our study shows that MRI of the ulnar nerve should be used in patients with clinical features of UNE especially in those with non-localizing neurophysiologic testing.

Adolescent↗
PubMed2002

The contribution of tremor studies to diagnosis of parkinsonian and essential tremor: a statistical evaluation.

This study statistically evaluated a set of commonly measured tremor parameters to determine their individual and combined ability to discriminate between essential tremor (ET) and Parkinsonian tremor (PT). Accelerometer and surface electromyographic (EMG) records of moderate to severe upper limb tremor in 20 patients with ET and 22 patients with PT were used to quantitatively compare tremor amplitude, frequency and pattern of muscle bursting in two resting and three non resting postures. The group statistics showed significant differences between ET and PT with respect to tremor frequency in all five postures, tremor amplitude at rest and muscle bursting patterns. Discriminant function analysis showed that no single parameter or combination of parameters was able to correctly classify all patients. Frequency was much more discriminating than amplitude or muscle bursting patterns in all limb postures. The best amplitude discrimination was obtained when the hand and forearm were both fully supported. Muscle bursting patterns were poorly discriminating and did not assist in correct classification of single patients. Group statistics confirmed a highly significant biological difference between the two tremor types. Optimal classification of single PT (86% correct) and ET (95% correct) patients was obtained using frequency and two selected amplitude parameters from the resting limb. Limb posture was an important variable in optimising the discriminative ability of tremor studies. The implications for routine tremor studies are summarised.

Adult↗
PubMed1998

Pretreatment and posttreatment positron emission tomographic scan imaging in a 20-year-old patient with Wilson's disease.

Wilson's disease is an autosomal-recessive inherited disorder that results in predominantly hepatic and neurologic manifestations. Neurologic abnormalities include tremor, ataxia, bradykinesia, rigidity, chorea, and dystonia. We report the clinical, radiologic, and serial FDG PET findings in a 20-year-old woman who presented with an asymmetric upper limb tremor caused by Wilson's disease. Reduced striatal and cerebral cortical glucose metabolism was demonstrated on a FDG PET study performed before the commencement of D-penicillamine therapy. After 6 months of treatment, the patient had shown only minimal clinical improvement, despite an increase in striatal and cerebral cortical glucose metabolism on a repeat FDG PET study. After 14 months of treatment, however, a moderate clinical improvement was noted and there was further increase in glucose metabolism on FDG PET.

Adult↗
PubMed1997

Clinical and neurophysiological features of tick paralysis.

The clinical and neurophysiological findings in six Australian children with generalized tick paralysis are described. Paralysis is usually caused by the mature female of the species Ixodes holocyclus. It most frequently occurs in the spring and summer months but can be seen at any time of year. Children aged 1-5 years are most commonly affected. The tick is usually found in the scalp, often behind the ear. The typical presentation is a prodrome followed by the development of an unsteady gait, and then ascending, symmetrical, flaccid paralysis. Early cranial nerve involvement is a feature, particularly the presence of both internal and external ophthalmoplegia. In contrast to the experience with North American ticks, worsening of paralysis in the 24-48 h following tick removal is common and the child must be carefully observed over this period. Death from respiratory failure was relatively common in the first half of the century and tick paralysis remains a potentially fatal condition. Respiratory support may be required for > 1 week but full recovery occurs. This is slow with several weeks passing before the child can walk unaided. Anti-toxin has a role in the treatment of seriously ill children but there is a high incidence of acute allergy and serum sickness. Neurophysiological studies reveal low-amplitude compound muscle action potentials with normal motor conduction velocities, normal sensory studies and normal response to repetitive stimulation. The biochemical structure of the toxin of I. holocyclus has not been fully characterized but there are many clinical, neurophysiological and experimental similarities to botulinum toxin.

Acetylcholine↗
PubMed1996

Brainstem myoclonus in a patient with non-dopa-responsive parkinsonism.

In the few reports where electrophysiologic techniques have been used to characterise stimulus-sensitive myoclonus in the setting of a parkinsonian syndrome, the origin of the myoclonus has usually been found to be cortical. We describe a patient with parkinsonism unresponsive to levodopa who had myoclonus that was both spontaneous and induced by somatosensory stimuli. In addition, autonomic symptoms and a marked sleep disturbance were present early in his illness. Results of electrophysiologic investigations including electromyography (EMG) studies, routine electroencephalography (EEG) recording, jerked locked back-averaging of EEG, and somatosensory evoked potentials were consistent with a brainstem origin for the myoclonic jerks. Following ipsilateral digital and supraorbital electrical stimulation, the earliest muscle activation occurred in the trapezius. An all-night sleep study showed frequent myoclonic jerks during sleep and markedly abnormal sleep architecture. We believe that this patient's myoclonus was related to pathologic changes in brainstem reticular nuclei that occurred as part of his disease process. To our knowledge, brainstem myoclonus has not been described as a feature of parkinsonian syndromes.

Brain Stem↗
PubMed1996

Apomorphine can increase cutaneous inhibition of motor activity in Parkinson's disease.

We studied the effect of non-nociceptive ipsilateral digital stimulation on EMG recorded from a small hand muscle before and after the administration of subcutaneous apomorphine in 6 patients with Parkinson's disease. All were receiving the drug to control ¿on-off¿ fluctuations in motor performance. Averaged rectified EMG was recorded from tonically contracted abductor pollicis brevis (APB) following index finger stimulation using a brief stimulus train. In 5 patients motor evoked potentials (MEPs) were also recorded from APB during tonic contraction. A conditioning stimulus train was applied to the index finger at intervals between 15 and 65 msec prior to the transcranial magnetic stimulus. After apomorphine administration the patient group showed a significant increase in both EMG and MEP inhibition induced by digital stimulation. In patients with Parkinson's disease who have marked motor fluctuations, the inhibitory response of upper limb motor neurones to low level digital cutaneous stimulation can be altered by dopamine agonists.

Aged↗
PubMed1994

Postural tremor of Parkinson's disease.

Previous studies have reported the resting tremor (RT) of Parkinson's disease to occur at frequencies between 3-7 Hz and to be characterised by an alternating pattern of electromyographic (EMG) bursting activity between opposing muscles. A postural tremor (PT), of higher frequency (> 6 Hz) and with a synchronous pattern of EMG activity, has also been previously described in Parkinson's disease. We investigated the electrophysiological and pharmacological properties of both the RT and PT of 11 patients with Parkinson's disease and 10 patients with essential tremor in a double-blind, placebo-controlled study of L-Dopa/benserazide and propranolol. Tremor amplitude and frequency were assessed via bidirectional accelerometry, and the pattern of activation of the antagonist muscles of the forearm was determined with use of surface EMG. In the Parkinson's disease group studied, the frequency, EMG pattern of bursts, and response to L-Dopa were similar for the two tremors (median improvement of RT by 70% and PT by 61%). Despite some overlap between the Parkinson's disease and essential tremor groups in the electrophysiology of the tremor, there was no such dramatic pharmacological response in the latter group. These results suggest that the RT and PT of Parkinson's disease share a common pathophysiology and are distinct from essential tremor.

Adult↗
PubMed1993

Mitochondrial encephalomyopathy: variable clinical expression within a single kindred.

The clinical manifestations of mitochondrial encephalomyopathy are described in four generations of a single kindred. The age of onset of major neurological disturbance varied from 3-70 years. In some patients, deafness was the only manifestation; in others, recurrent bouts of status epilepticus associated with focal neurological deficits and headache, caused severe disability or death. Examples of all three adult forms of mitochondrial encephalomyopathy: MELAS, MERFF and Kearns Sayre syndrome, were represented within the kindred. Associated features included deafness, short stature, non-insulin-dependent diabetes mellitus, migraine, peptic ulceration and severe constipation. The nt 3243 A-G MELAS mutation was detected in two members of the kindred. This study highlights the diversity of clinical expression of a mitochondrial mutation within a single kindred.

Adolescent↗
PubMed1993

Regional cerebral blood flow during memory recognition and neuropsychological performance in patients referred for investigation of dementia.

Regional cerebral blood flow was studied at rest and during a memory recognition activation task in a preliminary investigation carried out in patients with mild to moderate dementia of Alzheimer type and in 2 control groups of subjects. There were differences in the sites of activation-increased blood flows between the normal controls and the controls with major depression, while the Alzheimer's disease subjects showed more variable patterns of flow response, which differed overall from those present in the 2 control groups.

Alzheimer Disease↗
PubMed1992

Motor evoked potentials: a new method of controlled facilitation using quantitative surface EMG.

A new method of assessing MEP facilitation using surface EMG under computer control is described. Transcranial magnetic stimulation with voluntary contraction at a value between 2 and 6% of maximal surface EMG activity produced responses with shortest latencies and largest amplitudes and power. No significant changes occurred when facilitation increased beyond this level. These results are similar to previously published studies using a force transducer, confirming the reliability of the system as an alternative method of monitoring voluntary contraction. The controlling system may potentially provide an easy, flexible, quantitative method of ensuring adequate, reproducible facilitation with minimum EMG interference for testing in a clinical setting.

Electromyography↗
PubMed1992

Effect of ritanserin, a highly selective 5-HT2 receptor antagonist, on Parkinson's disease.

There is both experimental and clinical evidence to suggest a role for 5-hydroxytryptamine (5-HT) in Parkinson's disease. The effect of ritanserin, a highly selective 5-HT2 receptor antagonist, on Parkinsonian symptomatology was investigated in 10 patients in a single-blind placebo-controlled study. Akinesia and gait improved significantly in a dose-dependent manner in 5 and 7 patients respectively. However there was no significant improvement in tremor. The effects of ritanserin on akinesia and gait are consistent with a role for 5-HT in Parkinson's disease.

Aged↗
PubMed1991

Treatment of idiopathic spasmodic torticollis with botulinum toxin A: a double-blind study on twenty-three patients.

In a double-blind, placebo-controlled study, 23 patients suffering from intractable spasmodic torticollis (ST) were given successively either botulinum toxin A (BTA) or normal saline by intramuscular injections in the affected muscles. Evaluation was carried out by three blinded observers, using a clinical and video assessment of the severity of torticollis, employing a scoring system described by Tsui (1). Patients were also asked to subjectively comment on changes in the amount of pain and on changes in the activities of daily living (ADL). BTA was proven to be superior on all forms of assessment to placebo, and these results were statistically significant. Side effects mainly consisted of pain at the injection site. Tiredness occurred at equal frequency with BTA and placebo. No serious or systemic side effects were noted. Botulinum toxin is a safe, effective and relatively simple treatment for spasmodic torticollis.

Adolescent↗
PubMed1991

A comparison of standard Madopar and controlled release Madopar in Parkinson's disease.

In a randomised, double-blind cross-over study, objective measures were used to compare the effect of a single oral dose of a standard preparation of levodopa-benserazide (Madopar M) with a sustained-release preparation (Madopar HBS) in 9 Parkinsonian patients with 'end of dose deterioration'. The response of patients to an optimised regimen of each preparation was also assessed using a patient diary. In all patients the onset of effect of Madopar HBS following a single dose was delayed compared with Madopar M. The duration of effect of a single dose of Madopar HBS was substantially (38-120%) longer than Madopar M in five patients and the same or shorter in four patients. According to the patients' diaries, six patients noted an increase in 'on' hours while on Madopar HBS. The duration and severity of dyskinesia was similar for the two preparations. Madopar HBS is likely to be useful in some Parkinsonian patients with 'end of dose deterioration'. As the effect of each dose is delayed it is probably best given in combination with standard Madopar.

Adult↗