The correct combination
Case 134
【Discussion】As cognition disorder diseases, Alzheimer dementia, Lewy body dementia, frontotemporal dementia, cerebral vessel dementia, and normal pressure hydrocephalus (NPH) are listed. This week, we presented typical images of these diseases on MRI and/or CT. In short, volume loss of bilateral amygdala suggests Alzheimer dementia shown as Figure 2 and volume loss of hemi-lateral amygdala suggests transition to Alzheimer dementia as shown Figure 3. Volume loss of frontotemporal lobes suggests frontotemporal dementia as shown in Figure 4. No specific volume loss is acknowledged in Lewy body dementia. Namely, it suggests Lewy body dementia in the case of no volume loss of amygdala and frontotemporal lobe on CT or MRI (Fig. 5). Alcoholic dementia causes atrophy of the whole cerebral atrophy except cerebellum.
Meanwhile, the symptoms of NPH are characteristic of cognition impairment, gait disturbance (magnet walking) and urinary incontinence (1, 2). The imaging characteristics of NPH are as follows; dilatation of lateral, third ventricles and Evans ratio > 0.30; flow void of aqueduct on T2WI; narrow convexity sulcus on coronal and/or axial images on CT or T2WI; narrow angle of frontal horn on a coronal image (< 90°)(3, 4, 5). In our case of NPH as shown Figure 1, dilatation of lateral ventricle, third ventricle and aqueduct and narrow convexity sulcus were acknowledged, but not in flow void in aqueduct and in narrow angle of frontal horns.
Etiology of NPH is still not clarified but it is believed probably due to local impairment of absorption of cerebral spinal fluid (CSF) from arachnoid villi (1, 2). Pressure of CSF is maintained by the dilatation of lateral ventricle and third ventricle. The long term compression induces the damage of periventricular structure. Dilatation of lateral ventricle compresses the internal capsule and corona radiata, causing the impairment of pyramidal tract and leading to gait disturbance. Because the convexity sulcus is tight compared with other sulci on MRI or CT, impairment of CSF absorption at the convexity is doubted. The local compression of frontal lobe causes cortical or subcortical dysfunction of the frontal lobe. The frontal lobe functions intelligence including hold of urination and defecation. The compression and the stagnation of the waste product from frontal lobe induce urinary incontinence and cognition impairment (6).
The cognition impairment between frontotemporal dementia and NPH is similar but differs in urinary incontinence. The difference might be attributable to whether atrophy or compression damage of the frontal lobe, which is the future problem to be clarified (7).
【Summary】
We present five cases with Alzheimer dementia, transition to Alzheimer dementia, Lewy body dementia, frontotemporal dementia and normal pressure hydrocephalus (NPH). It is borne in mind that The imaging characteristics of NPH are ; dilatation of lateral, third ventricles and Evans ratio > 0.30; flow void of aqueduct on T2WI; narrow convexity sulcus on coronal and/or axial images on CT or T2WI; narrow angle of frontal horn on a coronal image (< 90°). NPH is caused by the impairment of absorption of CSF from the arachnoid villi at the convexity. The damage of internal capsule or corona radiata due to compression of ventricular dilatation causes gait disturbance and the compression and waste product stagnation of the frontal lobe cause urinary incontinence and cognition impairment.
【References】
1.Brean A, et al. "Prevalence of probable idiopathic normal pressure hydrocephalus in a Norwegian population". Acta Neurologica Scandinavica. 2008;118 : 48–53.
2.Tanaka N, et al. Prevalence of possible idiopathic normal-pressure hydrocephalus in Japan: the Osaki-Tajiri project. Neuroepidemiology. 2009; 32 : 171–175.
3.Damasceno, et al. "Neuroimaging in normal pressure hydrocephalus". Dementia & Neuropsychologia. 2015; 9 : 350–355.
4.Sasaki M, et al. Narrow CSF space at high convexity and high midline areas in idiopathic normal pressure hydrocephalus detected by axial and coronal MRI. Neuroradiology. 2008 Feb. 50(2):117-22.
5.Gyldensted C. Measurements of the normal ventricular system and hemispheric sulci of 100 adults with computed tomography. Neuroradiology. 1977 Dec 31. 14(4):183-92.
6.Sakakibara R, et al. Mechanism of bladder dysfunction in idiopathic normal pressure hydrocephalus. Neurourol Urodyn. 2008;27(6):507-10.
7.Kazui H, et al. Cognitive impairment in patients with idiopathic normal pressure hydrocephalus. Brain Nerve. 2008;60:225-231.
2018.12.19