Multiple diffusivities define white matter degeneration in amnestic mild cognitive impairment and Alzheimer's disease

Different diffusivity measurements in diffusion-tensor imaging (DTI) could be helpful for detecting the distinct mechanisms of white matter degeneration in Alzheimer's disease (AD). However, few studies have explored the changes of white matter in amnestic mild cognitive impairment (aMCI) and AD by whole-brain voxel-wise analyses of all diffusivity indices. The association between grey matter atrophy and white matter damage measured by distinct diffusivities is still uncertain. Structural magnetic resonance imaging and DTI with four diffusivity indices, comprising fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity, were performed in 30 normal controls, 26 mild AD patients, and 40 aMCI patients with isolated memory impairment. T1 voxel-based morphometry and DTI tract-based spatial statistics were applied to compare the grey and white matter changes in the 3 groups. In contrast to the lack of significant white matter change presenting in aMCI patients, extended white matter degeneration over entire cerebral networks was exhibited in mild AD patients. Both axonal degradation and demyelination contributed to the white matter degeneration in AD; nevertheless, demyelination essentially involved the frontal portion of cerebral networks. Axonal degradation and demyelination over the temporal region were associated with the contiguous grey matter atrophy. However, only the severity of demyelination over the frontal region was correlated with the degree of atrophy over adjacent frontal grey matter. Our results suggest that different mechanisms of white matter damage demonstrate discrete regional distribution in AD. Demyelination may independently correlate with contiguous grey matter over the frontal region.     

Brainstem 1H-MR spectroscopy in episodic and chronic migraine

The pathogenesis of evolution from episodic migraine (EM) to chronic migraine (CM) has not yet been clearly determined. Some studies revealed that dysfunction of the brainstem may play a role. We aimed to determine the brainstem ¹H-MR spectroscopic (MRS) findings in episodic and chronic migraine. We recruited patients with EM, CM and controls. Patients with CM were divided into subgroups with and without medication overuse (MO). The ¹H-MRS metabolite ratios at the periaqueductal gray (PAG) and bilateral dorsal pons were measured and compared with those in controls. A total of 19 patients with EM, 53 patients with CM (with MO n = 30, without MO n = 23) and 16 control subjects completed the study. Patients with EM had the highest N-acetylaspartate (NAA)/creatine (Cr) ratio at the dorsal pons (right, P = 0.014; left, P = 0.034) in comparison with those of CM and controls. The latter two groups did not differ. Among migraine patients, NAA/Cr ratios at dorsal pons were inversely correlated with headache frequency (right, r = −0.350, P = 0.004; left, r = −0.284, P = 0.019) and intensity (right, r = −0.286, P = 0.019; left, r = −0.244, P = 0.045), but not disease duration. In contrast, the metabolite ratios did not differ at the PAG among the study groups. Of note, MO was not associated with brainstem MRS ratios in patients with CM. The increased NAA/Cr levels may suggest neuronal hypertrophy at the dorsal pons in EM. A progressive dysfunction of this region may occur from EM to CM since the levels declined with increasing headache frequency and intensity.     

Short term vs. long term test–retest reproducibility of I-ADAM for the binding of serotonin transporters in the human brain

Previous brain imaging studies have demonstrated a seasonal difference of serotonin transporter (SERT) binding in the human brain. However, the results were somewhat contradictory. We conducted test–retest study with single photon emission computed tomography (SPECT) with ¹²³I-ADAM as ligand in 28 healthy subjects. Ten of the subjects were studied within 1 month, whereas 18 were randomly assigned to be studied over a period of up to 1 year. The primary measure was the specific uptake ratio (SUR). Regions of interest included the midbrain, thalamus, putamen and caudate. The intra-class correlation coefficient (ICC) was 0.52–0.94 across different brain regions over 1 month, whereas the ICC was - 0.24 – 0.63 over a 1 -year period. The 1 -month variability ranged from 6.5 ± 5.1% to 12.5 ± 10.6% across different brain regions, and the 1 -year variability ranged from 16.5 ± 9.6% to 41.9 ± 35.5%. The Kruskal–Wallis test revealed a significant difference of variability across months. The Wilcoxon Signed Ranks Test showed the SUR between test-retest scans was of borderline significance. Curve fitting, using a 4th degree polynomial model, revealed a significant circadian correlation between the variability and interval of test-retest measurements. Our findings demonstrate the test–retest reproducibility of ¹²³I-ADAM in different time periods and suggest that circadian variation of SERT levels in the human brain might exist.     

MR imaging of giant intracranial aneurysm.

We reviewed the clinical features and findings of magnetic resonance imaging (MRI) in 17 cases of giant intracranial aneurysm (GIA). All were confirmed by digital subtraction angiography (DSA). Seven were non-thrombosed and 10 were partially thrombosed.All thrombosed parts showed no enhancement. The majority of the lumen showed good enhancement in the post-contrast study (89%). About 80% of the partially thrombosed aneurysms had an onion skin appearance on non-contrast T1WI. On T2WI about 80% of partially thrombosed aneurysms had a low signal inside the thrombus or its wall from the susceptibility effect of blood elements such as haemosiderin. Flow void sign was noted in 88% on non-contrast T1WI and T2WI. Flow artifacts along the phase-encoding direction from the lumen of the aneurysm were noted in 41% of non-contrast T1WI, 56% of contrast-enhanced T1WI, and 29% of T2WI.Non-enhancement inside the thrombus and an onion skin appearance were important signs of thrombosis of the aneurysm. Flow artifacts along the phase-encoding direction from the lumen of the aneurysm provided an important clue of a patent lumen inside an aneurysm. The following signs provided clues to the diagnosis of patency lumen instead of thrombosis with high sensitivity and specificity: flow void sign on noncontrast T1WI (sensitivity 88%, specificity 100%), enhancement on contrast-enhanced T1WI (sensitivity 89%, specificity 100%), presence of either flow void sign or enhancement on contrast-enhanced T1WI (sensitivity 100%, specificity 100%).     

Gamma knife radiosurgery for the treatment of recurrent seizures after incomplete anterior temporal lobectomy

To evaluate the efficacy and safety of gamma knife radiosurgery (GKS) in treating temporal lobe epilepsy, GKS was performed in four adult patients with recurrent complex partial seizures who underwent incomplete anterior temporal lobectomy (ATL) but were reluctant to undergo a second resective surgery. A marginal dose of 24.5–25 Gy, corresponding to 65–70% isodose curve, was delivered to the treatment target that included the residual amygdala and the head and anterior body of the hippocampus.None of the patients had severe acute side effects but three patients had radiation-induced MRI signal changes around the target volume 13, 20, and 24 months after GKS, respectively. All four patients had significant seizure reduction during the first 6-month period and clinical efficacy persisted throughout the 2-year follow-up period. All of the patients also had improved neuropsychological profiles, including memory function and quality-of-life, compared to their pre-GKS conditions.In conclusion, the safety and clinical efficacy of GKS make it a reasonable and suitable therapeutic alternative for patients with recurrent seizures after incomplete ATL. A higher marginal dose of >25 Gy and wider coverage may be more clinically beneficial but warrant further investigation.     

Imaging of invasiveness of pituitary adenomas

The purpose of our study was to examine the tumor size, imaging invasiveness of the pituitary macroadenomas (PMA) and to evaluate the directions of PMA spread. One hundred and thirty-five patients with PMA were examined with MRI and/or CT for pre-operative evaluation. We retrospectively reviewed the CT and MRI to identify tumor size, extension and to evaluate the directions of tumor spread. One hundred and seventeen patients (87%) had suprasellar extension with compression of optic apparatuses, twelve patients (9%) had extension of tumor upward to hypothalamus and third ventricle. Infrasellar extension via the floor of the sella and sphenoid sinus was found in thirty-eight patients (28%), and further downward extension to ethmoid sinus, nasopharynx and/or skull base was depicted in five patients (4%). Twenty-two patients (16%) had lateral invasion to the cavernous sinus and associated cranial nerves. Temporal and frontal extensions were depicted in seven patients (5%) and six patients (4%), respectively. Five patients (4%) had posterior subtentorial extension to posterior fossa. Histologically, only two patients showed microscopic invasive features. There was no correlation between histologic features and imaging invasiveness. The PMA had the potential of multi-directional extension. This experience indicated any type of pituitary adenoma could invade surrounding structures. Suprasellar invasion was the most common direction of pituitary adenoma spread, followed by infrasellar, lateral, anterior and posterior routes.     

Spontaneous intracranial hypotension presenting as mental deterioration

A 55-year-old woman had new onset of postural headache followed by change of mental status 3 weeks later. Magnetic resonance imaging (MRI) of the brain and whole spine showed typical spontaneous intracranial hypotension (SIH) findings, bilateral subdural hematoma, and cerebrospinal fluid leakage over the T7-T9. Her headache and mentality improved after epidural blood patches. Early recognition and correct diagnosis are crucial for successful treatment in patients with SIH presenting with mental confusion.     

Sequential MRI studies of a patient with complex partial status--a case report

Complex partial status (CPS), the status epilepticus of complex partial seizure, is rarely seen in clinical practice. The clinical presentations of CPS are characterized by confusion, slowness in response, together with stereotypic or complex automatisms and occasional secondary generalization. The electroencephalographic findings of CPS reveal characteristic focal epileptiform activities of mesial temporal region. Magnetic resonance image (MRI) is the imaging method of choice for studying epilepsy, particularly when focus is in the temporal lobe. We report a 49-year-old female with diagnosis of viral encephalitis and clinical presentation of CPS. We present the sequential brain MRI findings at acute, subacute and chronic stages of this patient.