Luciana Pelosi

Motor and somatosensory evoked potentials in hereditary spastic paraplegia.

Motor evoked potentials (MEPs) from the arms and legs to transcranial stimulation of the motor cortex and somatosensory evoked potentials (SSEPs) from stimulation of the nerves of the arms and legs, were recorded in 11 patients with hereditary spastic paraplegia. Electrophysiological abnormalities were found to be distributed differently among the systems examined; the longer the pathway, the higher the incidence and severity of impairment. MEPs from the leg were either absent or clearly reduced or prolonged in all patients. Eight patients showed abnormal cortical SSEPs on stimulation of the leg (absent or reduced responses in four, slowed central conduction velocity in seven), but only two of these patients had abnormal MEPs from the arm (absent responses). Cortical SSEPs on stimulation of the median nerve were reduced in two patients. Mean values of amplitude and central conduction velocity for MEPs and SSEPs from the leg were significantly different between patients and controls. Such differences were not found for either MEPs or SSEPs from the arm. This distribution of abnormalities, which suggests a differential involvement of the spinal pathways, parallels the reported pathological pattern in which degeneration of axons is more common and severe in the motor and sensory fibres supplying the leg.

The Effect of Stimulus Frequency on Spinal and Scalp Somatosensory Evoked Potentials to Stimulation of Nerves in the Lower Limb

The effect of variation in the stimulus frequency on spinal and cortical somatosensory evoked potentials (SSEPs) to common peroneal nerve stimulation at the knee (CPN-K) and tibial nerve stimulation at the ankle (TN-A) was studied in 11 healthy subjects. Six stimulus frequencies, 0.7, 1.5, 3.0, 5.0, 7.0 and 10.0 Hz, were used in random order. With increasing stimulus rate spinal responses remained unchanged. By contrast, early cortical responses became significantly reduced in amplitude or undetectable for stimulation frequencies above 3.0 Hz for the CPN-K and 5.0 Hz for the TN-A. In 2 subjects the configuration and the latency of CPN-K SSEPs were affected by stimulus frequency. Similar changes were not observed in TN-A SSEPs.

Peripheral nerve ultrasound in cerebellar ataxia neuropathy vestibular areflexia syndrome (CANVAS)

We report preliminary findings of nerve ultrasound in patients with cerebellar ataxia neuropathy vestibular areflexia syndrome (CANVAS) who have sensory impairment due to dorsal root ganglionopathy.

Peripheral nerve ultrasound findings in mucolipidosis type 3

PurposeThe mucolipidoses are rare autosomal recessive lysosomal storage disorders. Neurologic involvement in these conditions is generally thought to be limited to cognitive delay and entrapment neuropathies (primarily carpal tunnel syndrome). We sought to evaluate peripheral nerves in this condition using nerve ultrasound.MethodsWe performed peripheral nerve ultrasound in two siblings with genetically confirmed mucolipidosis type 3 (alpha/beta).ResultsPeripheral nerves in mucolipidosis type 3 (alpha/beta) exhibit multifocal enlargement.ConclusionThe peripheral nerve ultrasound has a role in the evaluation of this, and possibly other lysosomal storage disorders.

Peripheral nerve ultrasound in Friedreich ataxia: Nerve Ultrasound in Friedreich Ataxia

Sensory impairment in Friedreich ataxia (FRDA) is generally accepted as being due to a ganglionopathy. The degree of contribution from axonal pathology remains a matter of debate. Nerve ultrasound may be able to differentiate these processes.

080 Electrodiagnostic and ultrasound correlates of clinical severity in ulnar neuropathy

Introduction This is a retrospective review of 135 consecutive patients (M:F=71:64, mean age 52.6 years; 141 arms) referred to our institution with ulnar neuropathy over a two year period. We analysed electrodiagnostic and ultrasound findings in relation to clinical severity. Methods All patients underwent electrodiagnostic (AAN) and ultrasound examination of the symptomatic ulnar nerve(s). Clinical severity was graded on a 4 point scale from ‘very mild’ (symptoms only) to ‘severe’ (sensory loss plus marked atrophy of ulnar-innervated hand muscles). Results In ‘very mild’ neuropathies, the number of abnormal electrodiagnostic and ultrasound studies was 2 and 11 respectively, out of 54; in ‘mild’ neuropathies 19 and 25 out of 40; in ‘moderate’, 23 and 24 out of 24; and in ‘severe’, 23 and 23 out of 23. In 25 arms, (18 of which were clinically ‘severe’ or ‘moderate’), electrophysiology was abnormal but non-localising. Ultrasound showed abnormally large cross-sectional area at the elbow in 22 and diffuse nerve enlargement in three. Ultrasound identified nerve subluxation in 24 (17%) neuropathies, 58% of which were ‘very mild’, 25% ‘mild’ and 17% ‘moderate’ or ‘severe’. Conclusion In patients with symptoms but no clinical signs, electrophysiological evidence of ulnar neuropathy was present in 3.7%, whereas abnormal nerve ultrasound, often associated with subluxation, was demonstrated in 20%. Ultrasound increased the diagnostic yield of electrophysiology in the ‘very mild’ and, to a lesser extent, the ‘mild’ neuropathies by a combined 11%, and localised the lesion in all ulnar neuropathies with abnormal but non-localising electrophysiology. Nerve subluxation was disproportionately represented amongst the clinically ‘very mild’ neuropathies with abnormal ultrasound.

Ulnar neuropathy with abnormal non-localizing electrophysiology: Clinical, electrophysiological and ultrasound findings

OBJECTIVE To systematically study demographic, clinical, electrophysiological and nerve ultrasound characteristics of ulnar neuropathy with abnormal non-localizing electrophysiology (NL-UN) and further define the utility of ultrasound over and above the conventional electro-diagnostic approach. METHOD NL-UNs were prospectively identified from 113 consecutive referrals with suspected ulnar neuropathy. All received electro-diagnostic tests and ulnar nerve ultrasound. NL-UN severity was graded using clinical and electrophysiological scales. RESULTS In 64 of 113 referrals, an ulnar mono- neuropathy was confirmed by electrophysiology. Sixteen of these 64 (25%) had NL-UN, predominantly males (14 out of 16 patients) with severe or moderate clinical and electrophysiological ratings. Ultrasound showed focal ulnar neuropathy at the elbow in 13 out of 16, and diffuse ulnar nerve abnormality in three, and identified a likely or possible causative mechanism in 11. CONCLUSION A significant proportion (a quarter) of ulnar neuropathies with abnormal electrophysiology were NL-UN, of heterogeneous etiology; the majority were males with significant disability and axonal loss. Ultrasound had a significant role in localization and classification that facilitated management. SIGNIFICANCE To our knowledge, this is the first systematic prospective study that analyzes the demographic, clinical, electrophysiological and ultrasound characteristics of NL-UN in a routine clinical neurophysiology setting.

S69. Peripheral nerve ultrasound in Friedreich’s ataxia

Introduction Sensory impairment in Friedreich’s ataxia (FRDA) is generally accepted as being due to a ganglionopathy. The degree of contribution from axonal pathology remains a matter of debate. Nerve ultrasound may be able to differentiate these processes. Methods The ultrasound cross-sectional area of median, ulnar, tibial and sural nerves of 8 patients with FRDA was compared with 8 age- and gender-matched healthy controls and with reference values in our population. Results The nerves of the patients with FRDA were significantly larger than healthy controls’ at all upper limb sites ( p 0.05 ) but not significantly different in the lower limbs. Conclusion Our findings add further weight to the theory that dorsal root ganglionopathy is not the sole cause of peripheral sensory loss in FRDA. Peripheral neuropathic processes are likely to also play a role.

F33. Cross sectional peripheral nerve area in canvas syndrome (cerebellar ataxia neuropathy vestibular areflexia syndrome)

Introduction Patients with Cerebellar Ataxia Neuropathy Vestibular Areflexia Syndrome (CANVAS) have sensory impairment due to dorsal root ganglionopathy. After preliminary findings of small nerves on ultrasound in CANVAS, we sought to systematically study a larger cohort of CANVAS patients to see if this is a feature of this ganglionopathy and thus distinct from the ultrasound findings in axonal neuropathy. Methods The ultrasound cross sectional area (CSA) of median and ulnar nerves of 14 CANVAS patients was compared with 14 age- and gender-matched healthy controls (HCONT) and 14 age-and gender-matched patients with acquired axonal neuropathy (PNCONT). The individual CSAs of CANVAS and PNCONT patients were also compared with the mean CSA of our reference population. Results The nerve CSA of CANVAS patients was significantly smaller than the CSA of both HCONT and PNCONT at all sites ( P > 2 SDs below a reference mean. Conclusion The small nerves in CANVAS probably reflect nerve thinning from axonal loss secondary to ganglion cell loss. This is in contradistinction to the ultrasound abnormality in PNCONT, in which the nerves are mildly enlarged. Our data show a role for ultrasound in the diagnosis of CANVAS ganglionopathy. This may also be applicable to sensory neuronopathy from other causes.

Peripheral nerve ultrasound in friedreich’s ataxia

Objectives To investigate peripheral nerve ultrasound findings in patients with Friedreich’s ataxia (FRDA) and their relationship to the complex neuropathology of the somatosensory system in this condition. Methods The ultrasound cross-sectional area of median and ulnar nerves at mid-forearm and mid-humerus level of eight non-diabetic FRDA patients (confirmed by GAA triplet expansion of the frataxin gene) were compared with eight age- and gender-matched healthy controls and with a reference population. All patients had sensory neuropathy with reduced or absent sensory action potentials on electrophysiological tests. Results The mean cross-sectional area of the FRDA patient group was significantly larger than that of the healthy control group at all sites (p<0.05) with maximal differences at mid-humerus level. Seven of the eight FRDA patients had cross-sectional area measurements>2 SDs above our reference mean at one or more sites. Conclusions The ultrasound finding of enlarged peripheral nerves in FRDA patients points to a structural abnormality at peripheral nerve level. This contrasts with the reduced cross-sectional area seen in the cerebellar ataxia, neuronopathy, vestibular areflexia syndrome (CANVAS) which is thought to be due to a pure sensory ganglionopathy (Pelosi et al, Muscle Nerve 2017, in press). While the specific pathophysiology in FRDA is unknown, nerve enlargement suggests, in agreement with recent neuropathological studies, that axonal loss from dorsal root ganglionopathy is not the sole mechanism underlying sensory neuropathy of FRDA. Myelin and/or stromal abnormality at peripheral nerve level may play a significant role.