Devon I. Rubin

Caffeine for the prevention and treatment of postdural puncture headache: debunking the myth.

Objective:Is caffeine effective in preventing and treating postdural puncture headache (PDPH)? Methods:The question was addressed with a structured evidence-based clinical neurologic practice review via videoconferencing between 3 academic institutions. Participants included consultant and resident neurologists, clinical epidemiologists, medical librarians, and clinical content experts. A critically appraised topic format was employed, starting with a clinical scenario and structured question. Participant groups at each of the 3 institutions independently devised search strategies, located and compiled the best evidence, performed critical appraisals, synthesized the results, summarized the evidence, provided commentary, and declared bottom-line conclusions. Results:Three directly relevant randomized controlled trial articles were selected as the best available evidence for the clinical questions. Two investigated caffeine [oral and intravenous (IV)] as PDPH prophylaxis and 1 (oral) as PDPH treatment. One additional quasirandomized trial (IV) and 1 open-label trial (IV) of caffeine for PDPH treatment were located by reviewing bibliographies. Articles describing the pharmacological basis for caffeine therapy were also identified. No valid pharmacological rationale for caffeine as an antinociceptive agent for PDPH exists. The clinical trials are few in number, small in sample size, methodologically weak or flawed, and either demonstrate no effectiveness, contradictory and conflicting results, or invalid answers. Conclusions:The wide endorsement for caffeine to prevent and treat PDPH found in textbooks and review articles appears to be unwarranted and insufficiently supported by the available pharmacological and clinical evidence.

Neuralgic amyotrophy: clinical features and diagnostic evaluation.

BACKGROUND–Neuralgic amyotrophy is an uncommon neurologic syndrome of unknown etiology involving the brachial plexus, which is manifest by shoulder and arm pain, weakness, and sensory loss. Because of the diversity and variability of the initial features and similarity to other neurologic and non-neurologic disorders, patients may initially present to internists, orthopedic surgeons, or pulmonologists, and may be initially diagnosed with an alternative disorder. REVIEW SUMMARY–Neuralgic amyotrophy occurs at an annual incidence rate of 1 to 2 cases per 100,000 population. The disorder is most common in adulthood, but patients of any age may be affected. Pain is the most common initial symptom and is followed by weakness and sensory loss in the distribution of a single nerve or diffuse regions of the brachial plexus. Although the exact etiology is unknown, many associated factors, such as immunizations, minor trauma, infectious diseases, pregnancy, and surgical procedures have been associated with the development of the disorder. Evaluation with electrodiagnostic and radiographic studies is useful in confirming the diagnosis and excluding alternative disorders. No treatment has been definitively proven to improve the course of the disorder; however, the overall prognosis is good, with approximately 90% of patients demonstrating significant improvement. CONCLUSIONS–Neuralgic amyotrophy is an important, potentially debilitating disorder, which may present to physicians in multiple specialties. Awareness of this disorder may preclude unnecessary testing or surgical procedures and can guide toward appropriate treatment with physical therapy. Counseling patients about the overall good prognosis can help appease patients’ anxiety about a more sinister diagnosis or course.

Angelman's syndrome: clinical and electroencephalographic findings

Angelmans syndrome is a rare genetic disorder characterized by developmental delay, craniofacial abnormalities, ataxia, paroxysmal laughter, and seizures. The diagnosis is suspected in infants who have the characteristic clinical features and electroencephalographic (EEG) abnormalities and is confirmed by the genetic identification of a maternally derived 15q11-13 deletion. We report on 3 patients with genetically confirmed Angelmans syndrome who had the characteristic clinical and EEG features. The EEGs demonstrated high-amplitude 2- to 3-Hz delta activity, with intermittent spike-and-slow-wave discharges maximal in the occipital region in 2 patients and generalized sharp-and-slow-wave discharges, occipital spikes, and electrographic status epilepticus during slow-wave sleep in the other patient. The findings of generalized high-amplitude delta slowing and occipital spike-and-wave discharges, facilitated by eye closure, in children with developmental delay and seizures suggest the diagnosis of Angelmans syndrome and should lead to genetic testing.

Subacute sensory neuropathy associated with Epstein–Barr virus

A 35‐year‐old man experienced severe sensory loss, pseudoathetosis, and areflexia during recovery from a severe viral illness. Sensory nerve action potentials were absent, motor conduction velocities were mildly slowed, and blink reflexes were normal. Magnetic resonance imaging (MRI) revealed abnormal signal within the central and dorsal aspects of the thoracic cord. Acute and convalescent Epstein–Barr virus (EBV) titers suggested EBV as the etiology. Subacute sensory neuropathy, with peripheral and central nervous system involvement, is a rare complication of EBV infection.

Alpha-lipoic acid may improve symptomatic diabetic polyneuropathy.

Objective:In patients with symptomatic diabetic polyneuropathy, is oral alpha-lipoic acid (ALA) effective in improving neuropathic symptoms compared with placebo? Methods:The question was addressed with a structured evidence-based clinical neurologic practice review via videoconferencing between 3 academic institutions. Participants included consultant and resident neurologists, clinical epidemiologists, medical librarians, and clinical content experts. A critically appraised topic format was employed, with a clinical scenario, structured question, search strategy, appraisal, results, summary of evidence, commentary, and bottom-line conclusions. Results:A single modestly valid randomized controlled trial demonstrated that oral ALA in doses of 600 mg, 1200 mg, and 1800 mg was effective in reducing neuropathic symptoms of diabetic distal symmetric polyneuropathy (DSP) at 5 weeks, as assessed by the Total Symptom Score (≥50% reduction), with number needed to treat (NNT) (95% CI) of 2.7 (1.8 to 5.8), 4.1 (2.3 to 20.2), and 3.2 (2.0 to 8.6), respectively. Adverse events, including nausea, vomiting, and vertigo, were identified but occurred most frequently with ALA doses of 1200 mg and 1800 mg. Overall, treatment emergent adverse events for ALA 600 mg were not significantly different than placebo, but ALA 1200 mg and 1800 mg had number needed to harm (95% CI) of 4.5 (2.4 to 31.0) and 3.0 (1.9 to 7.1), respectively. Conclusion:Oral ALA may improve neuropathic symptoms in diabetic DSP. A single modestly valid RCT demonstrated that 600 mg was an effective and well-tolerated dose, with NNT 2.7 to significantly reduce neuropathic pain symptoms over a 5-week period. ALAs role and place in an algorithm among other commonly prescribed oral treatments for symptomatic relief of neuropathic pain in diabetic DSP remains unclear.

Electrophysiologic findings in amyloid myopathy

Myopathy is an uncommon manifestation of systemic amyloidosis. A retrospective chart review of 17 patients seen between 1975 and 1997 with biopsy‐proven amyloid myopathy was performed to characterize the electrophysiologic features. Nerve conduction study abnormalities occurred in 14 of 17 patients (82%). The most common abnormality was a low peroneal and/or tibial compound muscle action potential amplitude (n = 9). Mild abnormalities also occurred in seven other nerves. Repetitive stimulation at 2 Hz in 10 nerves was normal. Electromyography demonstrated fibrillation potentials in 69% of muscles, most frequently in the gluteus medius (90%) and paraspinals (87%). The fibrillation potentials were sparse in 60%. Short‐duration, low‐amplitude motor unit potentials (MUPs) were found in 72% of the muscles examined, were mild in 81%, and were more common in proximal muscles. Long‐duration MUPs were found in 19% of muscles and a mixed population of MUPs in 4%. These findings are similar to those of common chronic, inflammatory myopathies.

Is exercise necessary with repetitive nerve stimulation in evaluating patients with suspected myasthenia gravis

We retrospectively evaluated the effect of exercise on the degree of decrement in ulnar, spinal accessory, and facial repetitive nerve stimulation (RNS) in 179 patients with myasthenia gravis (MG) to assess whether exercise increases the diagnostic yield of identifying significant decrements. The mean worsening of decrement following exercise was 1.9% (ulnar nerve), 1.9% (spinal accessory nerve), and 1.3% (facial nerve). Abnormal (≥10%) decrement solely following exercise occurred in the ulnar nerve in 7% of patients, accessory nerve in 5%, and facial nerve in 7%. When analyzed according to Myasthenia Gravis Foundation of America class of disease, the likelihood of producing ≥10% decrement only after exercise was greatest in class I MG with facial RNS and in class II and III generalized MG with ulnar and spinal accessory RNS. In all other disease stages, the likelihood of producing ≥10% decrement only after exercise was ≤7%. This study suggests that exercise increases the yield of diagnosis of MG by RNS in only a small percent of patients. Therefore, in most patients with suspected MG, RNS at rest is sufficient and the additional time required for prolonged postexercise RNS may be better spent in examining other muscle–nerve combinations. Muscle Nerve, 2006

Trigeminal nerve repetitive stimulation in myasthenia gravis.

The aim of this study was to evaluate the utility of repetitive nerve stimulation (RNS) of the trigeminal nerve in assessing patients with myasthenia gravis (MG). In 26 normal controls and 21 patients with myasthenia gravis (MG), 2‐Hz repetitive stimulation of the trigeminal nerve was performed using a monopolar needle for percutaneous nerve stimulation and recording over the surface of the masseter. In the MG patients, repetitive stimulation of the ulnar, spinal accessory, and facial nerves was also performed. The mean percent decrement in the compound muscle action potential (CMAP) amplitude among the different nerves at rest were: ulnar, 4.3%; spinal accessory, 10.1%; facial, 14%; and trigeminal, 17.3%. The facial nerve demonstrated abnormal decrement in 57% of all patients, compared with the spinal accessory (48%), trigeminal (43%), and ulnar (20%) nerves. All patients tolerated trigeminal RNS better than or as well as facial RNS. The study demonstrates that trigeminal RNS is a safe, reliable, efficient, and well‐tolerated technique that provides another cranial nerve–muscle combination that can be used to supplement repetitive stimulation of other limb or cranial nerves in the evaluation of patients with bulbar or generalized MG. Muscle Nerve 29: 591–596, 2004

Acute compartment syndrome of the leg following diagnostic electromyography

Acute compartment syndrome of the lower extremity is typically associated with some form of trauma, either fracture or blunt injury. Accurate diagnosis and urgent treatment of this condition is required for preservation of the viability of the limb. We report the case of a 73‐year‐old man who developed an acute compartment syndrome of the leg after diagnostic electromyography. Potential causes and treatment are discussed. Muscle Nerve 27: 374–377, 2003

Needle Electromyography: Basic Concepts and Patterns of Abnormalities

Needle electromyography (EMG) records electrical signals generated from muscle fibers and interprets the signals to characterize underlying pathologic changes that are occurring in motor units within muscles. Different types of spontaneously firing waveforms and motor unit potential changes occur with different neuromuscular disorders. The performance of reliable EMG studies depends on the technical skills of the physician in inserting, moving, recording with a needle electrode, and analyzing electric signals recorded from muscle. This article reviews the technique of needle EMG and recognition and interpretation of various EMG waveforms. The author presents several demonstrative videos at www.neurologic.theclinics.com.