Bashar Katirji

Incidence and mortality rates of myasthenia gravis and myasthenic crisis in US hospitals

Objective: To determine the incidence and mortality rates and predictors of death in myasthenia gravis (MG) and MG crisis in a large US cohort. Methods: Our cohort was identified from the Nationwide Inpatient Sample database for the years 2000 through 2005 using ICD-9-CM codes. MG crisis was identified by the principal diagnosis code or by the presence of respiratory failure. The incidence of MG was stratified by age, ethnicity, and gender. Multivariate logistic regression analysis was used to identify predictors of mortality in MG. For trend analyses of immune intervention, we used the Cochrane-Armitage test. Results: After data cleansing, 5,502 patients with MG were included. In women, the incidence of admission was two to three times higher during the first 5 decades. In men, the incidence of admission was higher during the sixth, seventh, and eighth decades. The annual incidence rate of MG was higher in black women (0.01 per 1,000 persons/year) compared to white women and white and black men (0.009, 0.008, and 0.007 per 1,000 persons/year). The overall in-hospital mortality rate was 2.2%, being higher in MG crisis (4.47%). Older age and respiratory failure were the predictors of death, with adjusted odds ratios of 9.28 (95% confidence interval [CI], 3.31, 26.0) and 3.58 (95% CI, 2.01, 6.38). The trend of IV immunoglobulin utilization has increased compared to plasma exchange and thymectomy (p < 0.0001). Conclusion: Myasthenia gravis (MG) is still a disease of young women and old men, as reflected by the hospital admission rates. In-hospital mortality of MG is low. Hospital utilization of IV immunoglobulin has significantly increased compared to plasma exchange and thymectomy.

Severe exacerbation of hepatitis C–associated vasculitic neuropathy following treatment with interferon alpha: A case report and literature review

Vasculitic neuropathy may occur in association with chronic hepatitis C infection. Interferon alpha (IFNα), an effective treatment for chronic hepatitis C, can precipitate or worsen autoimmune diseases. We report a patient with chronic hepatitis C and mild indolent vasculitic sensorimotor peripheral polyneuropathy, who developed severe mononeuropathy multiplex soon after IFNα was initiated, and review the literature on worsening vasculitic neuropathy after IFNα treatment for chronic hepatitis C. Care should be taken after starting patient with chronic hepatitis C–associated vasculitic neuropathy on IFNα, as there is evidence that IFNα may exacerbate the neuropathy.

Electrodiagnostic features of acute paralytic poliomyelitis associated with West Nile virus infection

West Nile virus (WNV) infection is a potentially fatal disease, with meningoencephalitis being its most common neurological manifestation. Guillain–Barré syndrome (GBS) has also been described, but acute paralytic poliomyelitis has only recently been recognized. We report the clinical and electrodiagnostic findings of five patients with WNV infection, who presented with acute paralytic poliomyelitis. Three patients manifested focal asymmetrical weakness, and two had rapid ascending quadriplegia mimicking GBS. Electrodiagnostic studies during the acute illness showed normal sensory nerve action potentials, compound motor action potentials of normal or reduced amplitude, and no slowing of nerve conduction velocities. Depending on the timing of the examination, fibrillation potentials were widespread, including in those with focal weakness. Cervical magnetic resonance imaging in one patient showed abnormal T2‐weighted signals in the spinal cord gray matter. On follow‐up, signs of clinical improvement were seen in one patient, whereas two remained quadriplegic and ventilator‐dependent 5 months after the onset. This report highlights the value of the electrodiagnostic studies in the diagnosis and prognosis of focal or generalized weakness due to acute paralytic poliomyelitis associated with WNV infection. Muscle Nerve 29: 376–380, 2004

Lumbrical and interossei recording in severe carpal tunnel syndrome

Patients with severe carpal tunnel syndrome (CTS) may occasionally have absent median motor and sensory responses; in these cases, it is not possible to accurately localize the median mononeuropathy to the wrist using standard electrodiagnostic tests. We prospectively investigated the use of comparing the median motor latency to the second lumbrical and the ulnar motor latency to the interossei muscles in 28 patient hands with severe CTS and absent median motor and sensory responses. We found a prolonged latency difference in 92.8%. Along with its use in mild CTS, study of the lumbrical‐interossei latency difference is helpful in patients with severe CTS with absent median motor and sensory responses.

Guillain-Barré syndrome after Cyclospora infection.

We present a patient who developed Guillain–Barré syndrome (GBS) after a Cyclospora‐induced diarrheal illness. We raise the possibility that Cyclospora is an infectious trigger for GBS in this patient. An active search for this agent in patients with GBS preceded by diarrheal illness is recommended.

Multifocal motor neuropathy presenting with respiratory failure

Multifocal motor neuropathy is a disorder characterized by slowly progressive asymmetrical limb weakness and multiple motor conduction blocks. We report a 56‐year‐old woman with this disorder who presented unusually with respiratory failure and who initially had absent responses to phrenic nerve stimulation bilaterally. The mechanism of the patients respiratory failure may have been chronic conduction blocks in the phrenic nerves leading to diaphragmatic weakness.

Electrodiagnostic approach to the patient with suspected neuromuscular junction disorder

The electrodiagnostic (EDX) examination in patients with suspected Neuromuscular Junction (NMJ) disorder constitutes the most advanced and complex type of EDX studies. Understanding the anatomy and physiology of neuromuscular transmission is prerequisite for the comprehension and planning of EDX studies in patients with suspected NMJ disorders. In addition to routine nerve conduction studies and conventional needle electromyography (EMG), the EDX studies, which are most useful in the diagnosis of NMJ disorders, include repetitive nerve stimulation and single fiber EMG.

Sensory sparing patterns and the sensory ratio in acute inflammatory demyelinating polyneuropathy.

The relative preservation (sparing) of sural sensory nerve action potentials (SNAPs) is a useful diagnostic finding in patients with acute inflammatory demyelinating polyneuropathy (AIDP). However, recording of sural SNAPs is not always technically feasible, especially in obese, edematous, or elderly individuals. Hence, we systematically evaluated the predictive values of the commonly employed SNAPs in the diagnosis of AIDP within 2 weeks from onset of symptoms. Sensory sparing patterns and sensory ratios of the sural, radial, median, and ulnar SNAPs of AIDP patients were included in a retrospective and blinded analysis, and compared to patients with diabetic polyneuropathy (DPN) and controls. Logistic regression models for the sural plus radial SNAPs/median plus ulnar SNAPs (sensory ratio) were constructed. A sural sparing pattern was present only in the AIDP group (34.4%, P < 0.001). A radial sparing pattern did not discriminate the AIDP from the DPN groups. The sural/radial sensory ratio was useful to ascertain DPN, but did not discriminate AIDP from controls. The sensory ratio was higher in AIDP compared to DPN and controls and was an independent predictor for AIDP. This study implies that the sensory ratio is a useful predictor for the diagnosis of AIDP and may substitute for sural sparing in technically difficult situations. Muscle Nerve, 2006

Isolated dropped head due to adult-onset nemaline myopathy treated by posterior fusion

Neck extensor muscle weakness causing dropped head is most commonly associated with myasthenia gravis, ALS, and paraspinous myopathy.1–3 Less often, myotonic dystrophy, facioscapulohumeral muscular dystrophy, hypothyroidism, chronic inflammatory demyelinating polyneuropathy, polymyositis/dermatomyositis, and inclusion body myositis are associated with dropped head.1 We describe a patient with isolated dropped head and no limb weakness due to adult-onset nemaline myopathy that improved with a posterior cervical spinal fusion.nnA 72-year-old man presented with a 10-year history of a progressive head drop. He denied limb weakness, diplopia, or imbalance. There was no family history of neuromuscular disorders. His physical examination revealed isolated neck extensor weakness with normal limb muscle strength (figure, A). Deep tendon reflexes and sensation were normal. Creatine kinase, thyroid-stimulating hormone, and acetylcholine receptor antibodies were normal or negative. Cervical spine MRI demonstrated multilevel degenerative changes. Sensory and motor …

Neuromuscular transmission defect caused by carbamazepine1

The clinical effect of carbamazepine (CBZ) on neuromuscular transmission is described in two children who presented in coma with diffuse hypotonia and areflexia following CBZ overdose. Repetitive nerve stimulation (RNS) showed a decremental response only at high‐frequency stimulation. With supportive care, the patients made an uneventful recovery. Follow‐up RNS was normal. This is the first report of a clinically evident neuromuscular transmission defect produced by CBZ. We postulate that CBZs known effect on decreasing sodium channel depolarization produced a defect in neuromuscular transmission. The report emphasizes the contribution of RNS in the evaluation of coma of uncertain etiology, particularly in cases of possible intoxication, and the potential for CBZ to compromise neuromuscular transmission in normal individuals or in patients with a decreased neuromuscular transmission safety factor.