Zsuzsanna Arányi

Effort-induced mirror movements: A study of transcallosal inhibition in humans

During sustained, fatiguing maximal voluntary contraction of muscles of one hand, muscles of the other hand gradually become activated also. Such effort-induced mirror movements indicate a decreased ability of the central nervous system (CNS) to selectively control individual muscles. We studied whether altered transcallosal inhibition (TCI) contributed to this phenomenon. TCI was determined in ten healthy subjects by measuring the ipsilateral silent period (iSP) and the contralateral silent period (cSP) during a sustained contraction of the abductor digiti minimi, induced by focal unihemispheric ipsilateral transcranial magnetic stimulation. Mirror movements occurred in all subjects in response to the effort. There was a bilateral increase in cSPs and a parallel increase in the iSP in the contralateral working muscle. In contrast, the iSP in the mirroring muscle remained unchanged, explained by a balance of increased crossed pyramidal inhibition (cSP) and decreased transcallosal inhibition. In finely tuned unimanual movements, mirroring activity of the contralateral hand is suppressed by TCI originating in the working hemisphere. During sustained, effortful contractions, the outflow of the contralateral hemisphere is increased due to reduced TCI. Effort-induced mirror contractions are thus the result of disinhibition of contralateral crossed projections rather than disinhibition of ipsilateral uncrossed pathways.

Ultrasonography of MADSAM neuropathy: Focal nerve enlargements at sites of existing and resolved conduction blocks

Using the emerging technique of peripheral nerve ultrasonography, multiple focal nerve swellings corresponding to sites of existing conduction blocks have been described in demyelinating polyneuropathies. We report two cases of multifocal acquired demyelinating sensory and motor neuropathy (MADSAM). In the first, multiple focal nerve enlargements were detected by ultrasound at sites of previous conduction blocks, well after complete clinical and electrophysiological resolution. In the second case, existing proximal conduction blocks could be localized by ultrasound. Our cases highlight the importance of nerve ultrasound in identifying conduction blocks and demonstrate that ultrasonographic morphological changes may outlast functional recovery in demyelinating neuropathies.

High-Resolution Ultrasonography of Peripheral Nerves: Measurements on 14 Nerve Segments in 56 Healthy Subjects and Reliability Assessments

PURPOSE The aim of this study was to assess different aspects of reliability in high-resolution ultrasonography (HRUS) of the peripheral nerves and to establish reference values for the most frequently examined nerve segments. MATERIALS AND METHODS A nerve size parameter, the cross-sectional area (CSA) of the C5, C6 and C7 cervical roots, the median, ulnar, radial, superficial radial, peroneal, tibial, and the sural nerves was measured using HRUS at a total of 14 predefined anatomical sites in two different cohorts of healthy subjects (n = 56), and the inter-rater, intra-rater and inter-equipment reliability of measurements was assessed. RESULTS The mean CSA of the 14 nerve segments ranged from 2 to 10 mm(2). The intra-rater, inter-rater and inter-equipment reliability was high with intraclass correlation coefficients of 0.93, 0.98, and 0.86, respectively. The CSA values showed no consistent correlation with age, height, and body weight, but males had significantly larger values than females for nerve segments on the arm after correcting for age, weight and height in multivariate analysis. CSA values did not differ when two independent cohorts were compared. CONCLUSION Peripheral nerve ultrasonography is a reliable and reproducible diagnostic method in the hands of experienced examiners. Normal values for several upper and lower extremity nerves are provided by our study.

Effect of discharge desynchronization on the size of motor evoked potentials: an analysis

OBJECTIVE Motor evoked potentials (MEPs) after transcranial magnetic brain stimulation (TMS) are smaller than CMAPs after peripheral nerve stimulation, because desynchronization of the TMS-induced motor neurone discharges occurs (i.e. MEP desynchronization). This desynchronization effect can be eliminated by use of the triple stimulation technique (TST; Brain 121 (1998) 437). The objective of this paper is to study the effect of discharge desynchronization on MEPs by comparing the size of MEP and TST responses. METHODS MEP and TST responses were obtained in 10 healthy subjects during isometric contractions of the abductor digiti minimi, during voluntary background contractions between 0% and 20% of maximal force, and using 3 different stimulus intensities. Additional data from other normals and from multiple sclerosis (MS) patients were obtained from previous studies. RESULTS MEPs were smaller than TST responses in all subjects and under all stimulating conditions, confirming the marked influence of desynchronization on MEPs. There was a linear relation between the amplitudes of MEPs vs. TST responses, independent of the degree of voluntary contraction and stimulus intensity. The slope of the regression equation was 0.66 on average, indicating that desynchronization reduced the MEP amplitude on average by one third, with marked inter-individual variations. A similar average proportion was found in MS patients. CONCLUSIONS The MEP size reduction induced by desynchronization is not influenced by the intensity of TMS and by the level of facilitatory voluntary background contractions. It is similar in healthy subjects and in MS patients, in whom increased desynchronization of central conduction was previously suggested to occur. Thus, the MEP size reduction observed may not parallel the actual amount of desynchronization.

Vestibular click-evoked myogenic potentials: sensitivity and factors determining abnormality in patients with multiple sclerosis

Vestibular evoked myogenic potential (VEMP) assesses the sacculo-spinal pathway. The aim of our study was to examine sensitivity and factors determining abnormality of VEMP, indicative of brainstem dysfunction, in patients with multiple sclerosis (MS). Thirty healthy subjects and 30 MS patients were examined. All healthy subjects showed a normal biphasic response. Twelve of the 30 MS patients (40%) had abnormal recordings. There was a significant difference between MS patients and control subjects with respect to P13 latency (longer in the MS group) and P13-N23 amplitude (lower in the MS group). VEMP abnormalities were statistically significantly related to the presence of brainstem demyelinative lesions and a weaker correlation was found with disease duration. Clinical signs of vestibular dysfunction at any point during the course of the disease did not seem to affect the chances of obtaining abnormal VEMPs. Although the sensitivity of VEMP in detecting abnormality in MS patients is relatively low, its significance is evident in that it is the only electrophysiological method that is able to detect dysfunction in central vestibular pathways. Multiple Sclerosis 2007; 13: 193–198. http://msj.sagepub.com

Miller Fisher syndrome: Brief overview and update with a focus on electrophysiological findings

Miller Fisher syndrome (MFS), a variant of the Guillain–Barré syndrome (GBS), is characterized by ophthalmoplegia, ataxia, and areflexia. The annual incidence is around one patient per one million population. The antiganglioside anti‐GQ1b IgG antibody has a role in the pathogenesis of the syndrome, especially of ophthalmoplegia. The presence of this antibody in the serum can be identified in over 80% of the patients, peaking in the first week, whereas albuminocytological dissociation in the cerebrospinal fluid (CSF) appears later. The most consistent electrophysiological findings in MFS are reduced sensory nerve action potentials and absent H reflexes. More variability is seen with F waves and various investigations involving cranial structures. Although there are usually no abnormalities in MFS by routine neuroimaging, in a few cases, contrast enhancement of nerve roots and signs of central nervous system involvement were described supporting the hypothesis of an anti‐GQ1b‐syndrome, a continuum involving GBS, MFS, and Bickerstaff’s brainstem encephalitis. Owing to the lack of randomized trials, treatments used for GBS (intravenous immunoglobulin and plasmapheresis) are usually applied, although from retrospective analyses, the outcome was similar between treated and untreated subjects. The outcome of MFS is usually good with case fatality of < 5%. In the few autopsy cases, macroscopic abnormalities were generally not seen in the nervous system. Microscopic examination of the peripheral nervous system (including cranial nerves) showed segmental demyelination with minimal perivascular infiltration with normal spinal cord and brain stem.

Dental Status and Oral Health of Patients with Epilepsy: An Epidemiologic Study

Summary:  Purpose: We performed a dental survey of epilepsy patients to examine their oral health by statistical means and to provide a guide for the dental treatment of these patients.

Superior sensitivity of motor over somatosensory evoked potentials in the diagnosis of cervical spondylotic myelopathy

Myelopathy secondary to cervical spondylosis is often a difficult clinical diagnosis. Furthermore, with the introduction of magnetic resonance imaging (MRI) an increasing number of patients are identified with spondylotic cervical spinal cord compression. We analyzed the value of functional assessment of the spinal cord by motor and sensory evoked potentials (MEP and SEP) in the detection of myelopathy, with special emphasis on the correlation of clinical and electrophysiological findings. Fifty‐one patients with at least some degree of spinal cord compression because of cervical spondylosis, as shown by MRI, were included in the study, grouped according to clinical symptoms. We found that patients who had no clinical symptoms whatsoever indicating myelopathy (they were referred to MRI examination mostly because of cervical radiculopathy), had in the large majority normal MEP and SEP findings. Patients with slight, unspecific and non‐confirmative symptoms without pyramidal signs had mostly abnormal MEP but normal SEP findings. This points to the superior sensitivity of MEP over SEP in detecting myelopathy in its early stages. Patients with obvious clinical signs of myelopathy, including pyramidal signs had both abnormal MEP and SEP findings. Altogether these findings may help clinicians in interpreting MRI signs of cervical spinal cord compression.

Different Patterns of Nerve Enlargement in Polyneuropathy Subtypes as Detected by Ultrasonography

The purpose of our study was to examine how the pathologic type of polyneuropathy affects nerve size as assessed by high-resolution ultrasonography with a 15 MHz transducer. Cross-sectional area (CSA) of the C5-C7 nerve roots and several upper and lower limb nerves at multiple sites was measured in 38 patients with acquired diffuse sensorimotor demyelinating or axonal polyneuropathy and in 34 healthy control subjects. Significant differences were found among the groups for all nerve and root segments: Both types of polyneuropathy are characterized by nerve enlargement in comparison to controls, but in different patterns. In demyelinating polyneuropathies, an additional degree of nerve thickening appears in proximal upper limb nerves and cervical nerve roots compared with axonal polyneuropathies. With respect to the other nerves, a similar degree of nerve enlargement was observed in both patient groups. These results highlight that ultrasonography may be a complementary tool in differentiating polyneuropathies.

Ultrasonography of ulnar neuropathy at the elbow: Axonal involvement leads to greater nerve swelling than demyelinating nerve lesion

OBJECTIVE To evaluate nerve size parameters measured by ultrasound in patients with ulnar neuropathy at the elbow (UNE) and to correlate them with the type of nerve lesion. METHODS The largest cross sectional area (CSA(max)) of the ulnar nerve around the elbow and the cubital-to-humeral nerve area ratio (CHR) were measured in 50 elbows with UNE and in 87 elbows of 50 healthy subjects. CSA(max) and CHR were compared between controls and patients with predominantly demyelinative and axonal nerve involvement. Subgroups of patients with pure sensory and mixed sensorimotor axonal lesion were also compared. RESULTS In patients with axonal nerve involvement, a significantly larger CSA(max) and CHR were found when compared to those with predominantly demyelinating nerve lesion; both groups differed significantly from healthy controls. CSA(max) values in patients with sensorimotor axonal lesion were significantly higher than in those with pure sensory axonal involvement. CONCLUSION CSA(max) and CHR highly correlate with the type of nerve pathology in UNE, with a significantly larger nerve swelling seen in axonal lesions, as compared to demyelinating lesions. SIGNIFICANCE In addition to helping in the localization of nerve lesion, ultrasonography may also reflect the type and degree of nerve lesion as assessed by electrophysiological means.