Christine Quinto

Open-ring imaging sign Highly specific for atypical brain demyelination

Objective: To test the specificity for demyelination of a new neuroimaging sign: contrast enhancement shaped as an open ring or a crescent circumscribed to the white matter. Background: Brain demyelination can cause ring enhancement mimicking neoplasm or infection on CT or MRI. Methods: A MEDLINE search of pathology-proved demyelination yielded 32 illustrated cases of ring-enhancing lesions published between 1981 and 1995. Controls consisted of the same number of published images of neoplasms and infections, pathology proved, and matched by year of publication, and age and gender of the patient. Two neuroradiologists read the images twice independently 1 year apart. Results: Interrater agreement was good (κ = 0.64 and 0.66 for either reading). Test-retest reliability was high (κ = 0.75 and 0.74 for either rater). The open-ring sign clearly distinguished demyelinating lesions from neoplasms and infections. For demyelination versus neoplasm or infection, the specificity of the reading by the first neuroradiologist was 93.8 (95% CI, 86 to 98), and that of the second was 84.4 (95% CI, 74 to 92). The likelihood ratio of demyelination versus neoplasm averaged 5.2, and versus infection, 17.2. That is, if the lesions had the same incidence in the population, in the presence of an open-ring sign demyelination would be five times more likely than neoplasm and 17 times more likely than infection. However, given the much higher incidence of neoplasms and infections, these lesions are still frequently responsible for open-ring enhancement. Conclusions: The open-ring sign is often present in large, contrast-enhancing demyelinating lesions and helps to differentiate them from neoplasms and infections.

Posttraumatic delayed sleep phase syndrome.

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Sensitive median-ulnar motor comparative techniques in carpal tunnel syndrome.

We describe two modified methods for median‐to‐ulnar motor conduction comparison in the diagnosis of median neuropathy at the wrist: the median–thenar to ulnar–thenar latency difference (TTLD), and the median–thenar to ulnar–hypothenar latency difference (THLD). We also describe an F‐wave ulnar‐to‐median comparative test, the F‐wave latency difference (FWLD). The abnormal cutoffs based upon 34 normal controls are: TTLD, 0.8 ms; THLD, 1.2 ms; FWLD, 0.6 ms. In 50 patients (79 hands) with clinically defined carpal tunnel syndrome and electrophysiological evidence of median neuropathy at the wrist (based upon a prolonged median nerve palm–wrist latency), the diagnostic sensitivities were: 95–98%, 85–88%, and 75–78%, respectively. These tests are therefore highly sensitive. They are easily performed and require minimal additional effort to incorporate into commonly used clinical electrodiagnostic routines. They may be advantageous when a concomitant polyneuropathy is present, and they may also help avoid technical pitfalls and aid in identification of anatomic variants.

Median and ulnar palm-wrist studies

OBJECTIVES Routine carpal tunnel electrodiagnosis frequently includes median (MPW) and ulnar (UPW) palm-wrist mixed nerve conduction latency determinations over 8 cm. Despite widespread use, normative palmar latency difference (PLD) and UPW values, and the relative utility of onset latency (OL) or peak latency (PL) measurements are controversial. The current study was conducted to determine normative values for these parameters. METHODS MPW and UPW studies were performed unilaterally in 33 normal controls. The PLD-OL and PLD-PL were calculated. The mean, range, standard deviation, and upper limits of normal were determined. 74 hands (50 patients) with both clinical and electrophysiologic median neuropathy were also studied. RESULTS The abnormal MPW and UPW cut-offs were both 1.8 ms (OL), and 2.3 ms (PL). The abnormal PLD cut-offs were 0.5 ms (OL and PL). Using either OL or PL, PLD parameters were similar within controls, and also within CTS patients. Using either OL or PL, UPW parameters were similar between controls and CTS patients. CONCLUSIONS An abnormal PLD cut-off of 0.5 is recommended. This is slightly higher than some prior recommendations, however it should minimize the likelihood of false positive studies. Onset and peak latency measurements are likely to have similar clinical utility.

Needle Cervical Root Stimulation May Be Complicated by Pneumothorax

It is possible to stimulate cervical nerve roots by inserting a monopolar needle electrode into the cervical paraspinal musculature lateral to the C5-C6 or C7-T1 interspaces. [1,2] The needle is advanced until the vertebral arch is reached, and then electrical stimulation is applied. We report a case of pneumothorax associated with this procedure and offer suggestions to minimize the likelihood of this complication. A 65-year-old petite woman with a previously biopsied left brachial plexus schwannoma was being evaluated preoperatively for evidence of brachial plexus dysfunction. Physical examination was unremarkable except for a palpable mass in the supraclavicular fossa. A CT confirmed this mass (Figure 1). Nerve conduction values were normal, including motor and sensory nerve conduction of the median, ulnar, and radial nerves, sensory nerve conduction of the lateral antebrachial cutaneous nerve, and F-wave studies. Cervical root stimulation was …

Median-ulnar anastomosis to thenar, hypothenar, and first dorsal interosseous muscles: Collision technique confirmation

Median‐ulnar anastomosis (Martin‐Gruber anastomosis; MGA) is traditionally diagnosed based upon changes in compound muscle action potential (CMAP) amplitude following proximal stimulation. We describe a rare patient with a MGA innervating thenar, hypothenar, and first dorsal interosseous muscles. Proximal stimulation, however, evoked CMAPs with striking changes in morphology and area but only minimal amplitude changes, due to concomitant diagnoses of carpal tunnel syndrome and polyneuropathy. Collision studies were therefore required for diagnostic confirmation of the MGA.

Accessory deep peroneal neuropathy: Collision technique diagnosis

Accessory deep peroneal nerve (ADPN), a common anatomic variant, is traditionally suspected when common peroneal nerve stimulation evokes a greater amplitude extensor digitorum brevis compound muscle action potential than deep peroneal nerve (DPN) stimulation. Posterolateral ankle stimulation over the ADPN is confirmatory. We report a rare patient with ADPN neuropathy in whom the collision technique was necessary to confirm the presence of an ADPN and to distinguish between neuropathy of the ADPN and the DPN.