H. Tsukamoto

Fibular nerve damage in knee dislocation: spectrum of ultrasound patterns.

At least 25% of knee dislocations are associated with common fibular nerve injury. Diagnosis is usually based on clinical and neurophysiological findings. We assessed the role of nerve ultrasound in common fibular nerve injury.

Ultrasound and neurophysiological correlation in common fibular nerve conduction block at fibular head

OBJECTIVE Ultrasound (US) and neurophysiological examination are useful tools in the evaluation of common fibular mononeuropathy. There is only a report comparing US and electrophysiological parameters in patients with common fibular nerve (CFN) conduction block at fibular head. We investigated the correlation between US and neurophysiologic findings in this condition. METHODS We retrospectively reviewed patients with CFN assessed in our lab during last 2 years. Each patient underwent to clinical, neurophysiological and ultrasound evaluations. Cross sectional area (CSA) of CFN at fibular head was assessed. RESULTS Twenty-four patients were included. Motor nerve conduction study showed a reduction of distal compound muscle action potential (CMAP) amplitude in 10 patients (mean 1.3 mV). US showed an increased CSA in 10 patients. Statistical analysis revealed a strong correlation between the increased CSA and the CMAP reduction of CFN. CONCLUSION Our data suggest that usually US examination is normal in CFN conduction block at fibular head. However the association with axonal damage is frequently accompanied by an increase of CSA. SIGNIFICANCE Ultrasound evaluation may represent a powerful diagnostic/prognostic tool in cases with CPN conduction block at fibular head because it usually shows normal pattern in pure conduction block and increase of CSA in associated axonal damage.

Segmental evaluation of the peripheral nerve using tibial nerve SEPs for the diagnosis of CIDP

OBJECTIVE SEPs can evaluate the proximal portion of the peripheral nerve, including the nerve root, which is preferentially involved in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We retrospectively investigated the utility of tibial nerve SEPs for the diagnosis of CIDP. METHODS Subjects were 12 clinically-defined CIDP patients and 17 patients with diabetic polyneuropathy (DPN). We segmentally evaluated the entire peripheral nerve using the N8, P15, and N21 components. We defined findings suggestive of proximal-dominant involvement (proximal-dominant findings), and investigated their frequency in both groups. RESULTS Ten out of 12 CIDP patients showed at least one of the proximal-dominant findings, whereas none of the DPN patients did, when appropriate parameters were selected. The sensitivity was higher than conventional electrodiagnostic criteria such as the European Federation of Neurological Societies/Peripheral Nerve Societies criteria (definite in 8/12). Both a proximal-dominant involvement in CIDP patients and a distal-dominant involvement in DPN patients were evident by the Z-score plots. CONCLUSIONS Tibial nerve SEPs were highly sensitive and specific, at least in comparison with DPN, measures for the diagnosis of CIDP. SIGNIFICANCE Segmental evaluation of the peripheral nerve using tibial nerve SEPs is expected as a promising tool to document proximal-dominant involvement in CIDP.

N10 component in median nerve somatosensory evoked potentials (SEPs) is not an antidromic motor potential.

OBJECTIVE To test the hypothesis that the N10 far-field potential in median nerve somatosensory evoked potentials is generated by the motor axons by examining patients with amyotrophic lateral sclerosis (ALS). METHODS Subjects were 5 ALS patients showing pronounced or complete denervation of median-innervated small hand muscles. We evaluated N10 over scalp, and proximal plexus volleys (PPVs) at lateral or anterior cervical electrode. RESULTS N10 and PPVs were definitely preserved for every ALS subject. N10 amplitudes of ALS subjects were even significantly larger than control subjects. In one ALS patient completely lacking motor axons, N10 was larger than the largest one among control subjects. CONCLUSIONS Present results clearly indicate that N10 is not predominantly generated by motor axons but by the whole median nerve dominated by sensory axons. We propose a theory that N10 is a junctional potential generated by the entrance of the median nerve into bone at the intervertebral foramen, producing a positive pole at the non-cephalic reference electrode. Significantly larger N10 in ALS subjects may be due to the lack of cancellation by slower motor axons. SIGNIFICANCE The hypothesis that N10 is generated by motor axons is refuted, and a new theory of its generation is presented.

Spread to the dorsal ulnar cutaneous branch: A pitfall during the routine antidromic sensory nerve conduction study of the ulnar nerve

OBJECTIVE To document the incidence and effects of a previously unreported pitfall during routine antidromic sensory nerve conduction study (SCS) of the ulnar nerve: the spread of the wrist stimulation to the dorsal ulnar cutaneous (DUC) branch. METHODS The subjects consisted of 20 healthy volunteers. An antidromic sensory nerve action potential (SNAP) was recorded over the proximal interphalangeal joint of the little finger, and the DUC response was monitored over the dorsum of hand to check for the occurrence of this spread. RESULTS The spread occurred in all subjects, which caused a 4-87% increase in the SNAP amplitude. The likelihood that this spread may occur during routine SCS varied among the subjects, and also within an individual subject depending on minute shifts of the stimulating site. Selective stimulation of the ulnar main trunk up to maximal intensity without spread to the DUC was not achieved despite every effort in two subjects. CONCLUSIONS This spread phenomenon may occur frequently during routine antidromic SCS, but would not be recognized without monitoring the DUC response. SIGNIFICANCE This pitfall may interfere with the reproducibility of the SNAP amplitude, and also with the diagnosis of ulnar neuropathy at the wrist.

US diagnosis of sciatic nerve tumor proximal to gluteal fold

High-resolution ultrasound (US) is a helpful technique for the evaluation of peripheral nerves. It is now well accepted that especially in nerve mononeuropaties the combination of morphological data, obtained through US, and functional data, obtained through electrophysiology, is the appropriate way to reach the best diagnosis including information for therapeutical decision. Literature data show that US may crucially influence diagnosis and clinical care in nerve tumors [1, 2]. However, nerve US has some limitations. In particular the visualization of deep nerves is difficult, especially in overweight people. This is the case of proximal part of sciatic nerve that is commonly detectable only distal to the gluteal fold. We report on a 48-year-old woman complaining of pain and electric shocks radiated to sciatic course and trigger point in the right gluteal region. Clinical examination showed only mild right extensor hallucis longus weakness. Needle electromyography of tibialis anterior, gastrocnemius, peroneus longus was normal and mild chronic neurogenic recruitment was observed in extensor hallucis longus. It was suspected a right L5 radiculopathy but magnetic resonance (MR) showed only a mild L5–S1 bulging that was not considered the cause of symptoms. US of sciatic nerve was then performed although the trigger point was in a region where usually sciatic nerve is not detectable, proximally to the gluteal fold. US was performed using a linear 6–10 and 10–18 MHz transducer and sciatic nerve was bilaterally evaluated in distal–proximal direction starting from the popliteal fossa. Right sciatic nerve was detectable along all its course, even proximally to the gluteal fold although with no optimal visualization. At the middle-third of the gluteus a fusiform hypoechoic increase of nerve volume was found. The maximum longitudinal diameter was 2.5 cm and maximum antero-posterior diameter was 2.0 cm (max cross-sectional area 4.5 cm). An accurate evaluation of the US video clip suggested that the mass raised from lateral fascicles sparing and dislocating remaining medial fascicles (Fig. 1a, b). US and clinical data suggested a sciatic nerve tumor, likely a schwannoma. MR confirmed the lesion showing a partially preserved fascicular structure, suggesting a schwannoma (Fig. 1c–f). Surgical excision was refused by the patient and US monitoring planned. Our case report confirms the usefulness of US in the diagnosis of nerve tumors. US is not able to clearly differentiate the type of nerve tumor but can provide useful information to discriminate between the two main types, schwannoma or neurofibroma [3–5]. Schwannoma typically displaces the nerve fascicles and generally is positioned eccentrically to the affected nerve segment. Another typical feature especially of large lesions is the presence of hyperechoic calcifications and internal degenerative cystic foci. On the other side neurofibroma presents as a concentric lesion that does not displace the fascicular elements of the nerve but interferes with them (usually fascicles are not detectable). Another typical sonographic feature of this kind of tumor is the so-called ‘‘target sign’’ (layered aspect, with a hyperechoic centre and a peripheral hypoechoic rim, best seen on transverse scans) [6]. Usually G. Granata (&) I. Paolasso C. Erra H. Tsukamoto L. Padua Institute of Neurology, Catholic University of Sacred Heart, Largo F. Vito 1, 00168 Rome, Italy e-mail: granata.gius@gmail.com

O2-6-21. Comparison of muscle ultrasound findings between demyelinating neuropathy and axonopathy

Denervation causes increased echo intensity (EI) and decreased muscle thickness (MT) on muscle ultrasound (MUS). Chronic inflammatory demyelinating polyneuropathy (CIDP) does not present with denervation unless secondary axonal degeneration occurs. Hence, few MUS changes would occur compared to amyotrophic lateral sclerosis (ALS). The abductor pollicis brevis, abductor digiti minimi, and first dorsal interosseous muscles of 12 patients with CIDP and 13 patients with ALS were examined. There were no significant differences in Medical Research Council scales of each muscle between the CIDP and ALS group. EI and MT were measured quantitatively in every muscle. Raw values were converted into z-scores using the data from 40 normal controls (NCs). There were no significant differences between the CIDP and NC groups regarding EI and MT. The ALS group exhibited significantly higher EI and significantly lower MT than the other two groups (all P

Posterior interosseous nerve syndrome due to radioulnar joint cyst

1. Oh SJ, Kurokawa K, Claussen GC, Ryan H. Electrophysiological diagnostic criteria of Lambert-Eaton myasthenic syndrome. Muscle Nerve 2005;32:515–520. 2. Lennon VA. Serologic profile of myasthenia gravis and distinction from the Lambert-Eaton myasthenic syndrome. Neurology 1997;48:S23–S27. 3. Lennon VA, Kryzer TJ, Griesmann GE, O’Suilleahain PE, Windebank AJ, Woopmann A, et al. Calcium-channel antibodies in LambertEaton syndrome. Neurology 1995;332:1467–1474. 4. Oh SJ, Sher E. MG and LEMS overlap syndrome: case report with electrophysiological and immunological evidence. Clin Neurophysiol 2005;116:1167–1171. 5. Matsumoto R, Motomuira M, Yoshimura T, Kohara N, Kato T. Myasthenia gravis with electrophysiological features of Lambert-Eaton myasthenic syndrome: Usefulness of serum autoantibodies assay and neuromuscular biopsy. Clin Neurol 1999;39:531–537. 6. Brenna A, Curto N, D’Urso D, D’Avanzo F. Neuromuscular transmission disorder: combined myasthenia gravis and LambertEaton syndrome in one patient. J Neurol Neurosurg Psychiatry 1989; 52:684–685. 7. Sha S, Layzer R. Myasthenia gravis and Lambert-Eaton myasthenic syndrome in the same patient. Muscle Nerve 2007;36:115–117. 8. Lee HW, Shin HY, Kim SM, Sunwoo IN. A case of Lambert-Eaton myasthenic syndrome with small-cell lung cancer and transient increase in anti-acetylcholine-receptor antibody titer. J Clin Neurol 2012;8:305– 307. 9. Bastra I, Nikolic A, Loen M, Martinez-Martinez P, Stojanovic V, Larnic S, et al. MuSK myasthenia gravis and Lambert-Eaton myasthenic syndrome presenting as acute respiratory failure. Clin Neurol Neurosurg 2012;114:795–797.

P5.7 Activity dependent conduction block and distal conduction disturbance after exercise in anti-MAG neuropathy

Methods: We retrospectively reviewed clinical, electrophysiological and MRI findings of two CIDP patients. Results: Quadriparesis predominating in lower extremities began 3 weeks ago in the 33-year-old female and 10 days before in the 58 years-old male patient. Both showed albuminocytological dissociation on cerebrospinal fluid examination. Although nerve conduction studies did not reveal any demiyelinating findings, needle EMG showed reduced recruitment. Lower extremity somatosensorial evoked potentials (SEP) could not be recorded in both patients. Spinal MRI of both patients demonstrated thickened and marked enhancement of lumbosacral nerve roots. They received 0.4 gr/kg/day dose intravenous immunoglobulin (IVIG) for 5 days. Progression halted only for ten days and began again in the first patient. A second dosing of IVIG was ineffective and progression continued. The second patient showed a partial improvement for 7 months, followed by two exacerbations in three months. 1 mg/kg oral prednisolone was started in both patients and followed by almost complete recovery in six months. Conclusion: In spite of normal nerve conduction studies, exacerbations after onset of symptoms, or ongoing progression over at least two months, albuminocytological dissociation and nerve root enhancement on spinal MRI should suggest treatable polyneuropathies, like CIDP.

P21-26 Distal conduction disturbance after post exercise in anti-MAG neuropathy

are compatible with prolonged action potential and delay repolarization in traditional neurophysiological study. One of the patients suffered from severe cramp in hands especially in the winter and difficulty in writing and housework, others are no obvious problems in daily activities. The recovery cycles test on this patient showed prominently increasing in superexcitabilities and prolonged period of superexciability. Conclusion: Nerve excitability tests might contribute the direct of indirect information about ion channel function, including nerve and muscle.