Functional

Brain Structure and Function in Patients after Metal-on-Metal Hip Resurfacing

Editor’s Choice

September 2014

(2 of 3)

Malfunction of metal-on-metal hip prostheses may produce visual, hearing, and motor deficits. These authors compared brain volumes, metal deposition, and gray matter attenuation in 2 groups of patients 8 years after surgery. Whole blood cobalt and chromium levels were higher in patients with metal-on-metal prostheses and associated with subtle structural changes in the visual pathways and basal ganglia.

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Abstract

BACKGROUND AND PURPOSE
Hip prostheses that use a metal-on-metal articulation expose the brain to elevated metal concentrations that, in acute excess due to prosthesis malfunction, is associated with neurologic damage, including visual and hearing loss and motor deficits. Here, we examined whether chronic exposure to lower elevated metal levels, typical of well-functioning prostheses, also affects brain structure and function.

MATERIALS AND METHODS
We compared brain volumes, metal deposition, and gray matter attenuation by MR imaging and clinical neurologic function in patients 8 years after receiving a metal-on-metal hip resurfacing versus a matched group of patients with the same duration exposure to a conventional hip prosthesis.

RESULTS
Twenty-nine patients (25 men; mean, age 59 ± 7 years) after metal-on-metal hip resurfacing and 29 patients (25 men; 59 ± 8 years) after total hip arthroplasty were compared. Whole blood cobalt and chromium concentrations were 5–10 times higher in the metal-on-metal hip resurfacing group (P < .0001). Occipital cortex gray matter attenuation tended to be lower (P < .005 uncorrected, P > .05 corrected), and the optic chiasm area tended to be lower (mean difference, −2.7 mm2; P = .076) in the metal-on-metal hip resurfacing group. Subgroup analyses in 34 patients (17 per group), after exclusion of primary ocular pathology, showed the same trend in gray matter attenuation in the occipital cortex and basal ganglia and a smaller optic chiasm in the metal-on-metal

Crossed Cerebellar Diaschisis

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A 41-year-old female with history of migraine presented to the ED with acute onset of aphasia. In addition to the aphasia, there was numbness and tingling in the right arm and face. Patient demonstrated expressive aphasia and was not able to answer questions posed in the ED. Gadolinium MR perfusion images demonstrated decreased relative cerebral blood flow (top) in the left parietal/occipital lobes and increased time-to-peak (bottom) in the contralateral cerebellar hemisphere. Although crossed cerebellar diaschisis (CCD) is seen mostly on radiotracer studies (hypometabolism on PET studies), it was nicely demonstrated in our patient. CCD occurs more often after supratentorial infarctions but has been reported in the setting of migraine. This phenomenon occurs immediately after brain injury due to the large number of functional connections between cerebrum and cerebellum. In reverse CCD, the brain abnormality is due to injury of the cerebellum. Because of the limited number of slices on perfusion MR studies, particularly when using ASL techniques, it is important to keep in mind that the cerebellum may be involved in several supratentorial abnormalities and needs to be included in the study.  I would be interested in finding out if anyone else has seen this type of migraine-associated CCD.…

Mass in Septum Pellucidum

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Does anyone know what this mass could be? It was biopsied 2 years ago and pathology reported it as  “normal brain tissue”.

As you can see, the lesion is hyperintense on T2, hypointense on T1 and does not enhance.  No calcifications are present and no there is no restricted diffusion .

The patient is 25  year old and has loss of short term memory and seizures.

Any input into the nature of the mass is welcome.…

ADC Question

I will like to know if someone can help me with some doubts I have regarding ADCs.

1.  I have  a sample with some ADC values obtained in 1,5 T and others obtained in 3T ( same b value). Can I use the ADC values for statistics or do you think that they cannot be compared?

2.  Are the ADC values obtained using a diffusion sequence  the same that the ADC values obtained in a DTI sequence with 12 directions?

Thank you in advance.…

AJNR Paper Points to Future of Severe Ischemic Stroke Treatment

Acute ischemic stroke remains the most important neurologic malady in the world.  Severe strokes caused by artery occlusion are a minority of all strokes, but cause most of the poor outcomes and costs associated with stroke.  Neurointerventionalists have effective therapies, but too few  stroke patients undergo endovascular procedures.  The reasons are multiple, but a major reason is that patients too frequently arrive beyond the traditional time windows for treatment.  A way to break out of this dilemma is described in the paper recently ePublished in the AJNR (N. Janjua, A. El-Gengaihy, J. Pile-Spellman, and A.I. Qureshi AJNR Am J Neuroradiol first published on February 4, 2009 as doi: 10.3174/ajnr.A1474).

The paper describes a small series of patients who were outside of the traditional stroke therapy window, but underwent endovascular therapy anyway. The majority of the patients had small DWI abnormalities in the setting of significant neurological symptoms (NIHSS greater than 8), a circumstance that has been termed a clinical-diffusion mismatch. Of those who underwent successful revascularization, all had significant clinical improvement, and none had intracerebral hemorrhage. The data makes physiological sense. Patients with major artery occlusions, severe neurological symptoms and small diffusion abormalities must have excellent collateral circulation that is sustaining neuronal viability despite synaptic dysfunction that produces the neurological syndrome.

If the findings described by Janjua et al. are confirmed, it begs the question of how many potential patients may fit the clinical-diffusion mismatch criteria.  The number may be quite large as data from another paper by Copen et al. that was also recently ePublished (Existence of the Diffusion-Perfusion Mismatch within 24 Hours after Onset of Acute Stroke: Dependence on Proximal Arterial Occlusion Radiology. 2009 Jan 21. [Epub ahead of print]).  Copen et al. found that …

White Matter Tract Section

I have been asked by several invididuals to place more emphasis on articles that relate to the functional aspects of neuroimaging.  One of these topics are the the white matter tracts.  Starting later this year, AJNR will carry a bimonthly feature on the white matter tracts.  Drs. Naidich and Fatterpekar from the Mount Sinai Hospital in NYC will be in charge of this feature.  These short contributions will describe not only the anatomy of specific tracts, their DTI appearance but also their functional connections and the clinical symptoms produced when they are injured.  I look forward to their contributions which undoubtedly will enrich all us.…