A repeating fast radio burst source localized to a nearby spiral galaxy.

Fast radio bursts (FRBs) are brief, bright, extragalactic radio flashes1,2. Their physical origin remains unknown, but dozens of possible models have been postulated3. Some FRB sources exhibit repeat bursts4-7. Although over a hundred FRB sources have been discovered8, only four have been localized and associated with a host galaxy9-12, and just one of these four is known to emit repeating FRBs9. The properties of the host galaxies, and the local environments of FRBs, could provide important clues about their physical origins. The first known repeating FRB, however, was localized to a low-metallicity, irregular dwarf galaxy, and the apparently non-repeating sources were localized to higher-metallicity, massive elliptical or star-forming galaxies, suggesting that perhaps the repeating and apparently non-repeating sources could have distinct physical origins. Here we report the precise localization of a second repeating FRB source6, FRB 180916.J0158+65, to a star-forming region in a nearby (redshift 0.0337 ± 0.0002) massive spiral galaxy, whose properties and proximity distinguish it from all known hosts. The lack of both a comparably luminous persistent radio counterpart and a high Faraday rotation measure6 further distinguish the local environment of FRB 180916.J0158+65 from that of the single previously localized repeating FRB source, FRB 121102. This suggests that repeating FRBs may have a wide range of luminosities, and originate from diverse host galaxies and local environments.

Pathologic changes associated with intracranial hypotension and meningeal enhancement on MRI.

We report a patient with a 6-week history of postural headache due to intracranial hypotension whose MRI revealed findings typical of this syndrome, including diffuse meningeal enhancement following gadolinium infusion. Biopsy revealed extensive fibrocollagenous proliferation in the leptomeninges without evidence of inflammation. The pathologic changes in this patient, which occurred soon after the onset of symptoms, are probably related to the striking meningeal enhancement seen in this syndrome.

Visualization of brain iron by mid-field MR.

Brain iron was visualized on a mid-field (0.5 T) scanner using a spin-echo pulse sequence. Methemoglobin was hyperintense on T1- and T2-weighted images. Deoxyhemoglobin, hemosiderin, and ferritin were seen as decreased intensity on T2-weighted images. The spin-echo pulse sequences were improved for identification of deoxyhemoglobin, hemosiderin, and ferritin by prolonging the TR to 3000 msec and the TE to 80-120 msec. Phase-encoding artifacts at the level of the sylvian fissures caused increased noise, obscuring the brain iron in the lentiform nuclei with the TE of 120 msec. This artifact was substantially reduced or eliminated by lowering the TE to 80 msec, changing the phase-encoding gradient to the Y axis, or using additional pulsing in the slice and read gradients. Use of either the improved spin-echo or gradient-echo pulse sequences on a mid-field MR scanner provides improved evaluation of brain iron.

Quantitative measurement of neurologic impairment in patients with multiple sclerosis.

Eleven patients with clinically diagnosed multiple sclerosis were simultaneously evaluated with history, physical, and neurologic evaluations and a series of objective neurophysiologic tests. Patients were then scored independently on clinical stage of their disease using a system based on symptoms in history or findings on physical or neurologic examination. Test scores on objective tests were compared with clinical scores with each evaluator. Patients with high test scores on clinical evaluation usually had high test scores on objective testing. Symptoms and physical findings were then correlated with abnormalities on objective tests. Objective abnormalities in visual evoked response and auditory evoked response on several occasions preceded the development of symptoms. All patients except for two had more than one abnormality on objective testing, suggesting a high likelihood that objective tests are helpful in the diagnosis of early-stage multiple sclerosis.

Indications for echocardiography in patients with ischemic stroke.

The recent availability of two-dimensional echocardiography (2DE) has fostered the expectation that cardiac embolic sources could be identified or excluded with certitude in ischemic stroke patients. As a screening procedure, 2DE has had a low yield. In selected patients, 2DE holds promise as a useful diagnostic test. Stroke patients who may benefit from 2DE include patients under age 45, patients with suspected left atrial myxoma, and patients with known infective endocarditis, prosthetic heart valves, or rheumatic valvular heart disease. In patients with ischemic heart disease, the yield of useful information from 2DE will be low but may, on occasion, influence management.

Echocardiography in diagnostic assessment of stroke.

We assessed the use of echocardiography in the evaluation of stroke by recording M-mode and two-dimensional (2D) echocardiograms in 100 consecutive hospitalized patients. Of the 95 persons satisfactorily imaged with 2D echocardiography, 47 lacked clinical and routine laboratory evidence of heart disease; no potential embolic source or other finding that altered therapy was diagnosed by echocardiography. In the remaining 48 patients with clinical or routine laboratory evidence of heart disease, two with left ventricular thrombus as a potential embolic source were identified by 2D echocardiography. M-mode echocardiograms failed to detect the thrombus in either patient. No patients with left atrial thrombi, mitral stenosis, cardiac tumor, or vegetations suggesting endocarditis were identified. One patient had possible mitral valve prolapse. Echocardiograms in patients lacking other available evidence of heart disease are unlikely to yield findings that alter the clinical approach to patients with stroke; echocardiography in stroke patients with clinically evident heart disease may have greater clinical utility; additional study of the role of echocardiography in selected subgroups of stroke patients is indicated.