MR volumetric changes after diagnostic CSF removal in normal pressure hydrocephalus

Abstract

Although diagnostic CSF removal in patients with suspected normal pressure hydrocephalus (NPH) is performed frequently, its impact on changes of the global brain volume and volume of the ventricles has not been studied in detail. We examined 20 patients with clinical and radiological signs of NPH. These received MRI prior to and immediately after diagnostic CSF removal, either via lumbar puncture (TAP, n = 10) or via external lumbar drainage (ELD, n = 10). Changes in global brain volume were assessed using SIENA, a tool from the FSL software library. Additionally, we determined the change of the lateral ventricles' volume by manual segmentation. Furthermore, we recorded systematic clinical assessments of the key features of NPH. The median volume of CSF removed was 35 ml in TAP patients and 406 ml in ELD patients. Changes in global brain volume were found in both patient groups. Brain volume change was significantly larger in ELD patients than in TAP patients (p = 0.022), and correlated with the volume of CSF removal (r = 0.628, p = 0.004). Brain volume expansion was most pronounced adjacent to the lateral ventricles, but also detectable in the temporal and frontal regions. The median ventricular volume decreased after CSF removal. Ventricular volume reduction was more pronounced in ELD patients than in TAP patients. This study quantifies for the first time immediate volumetric changes of global brain tissue and of ventricles after diagnostic CSF removal in NPH patients. In particular, we report evidence that CSF removal results in a change of the brain volume rather than only a change of the brain's shape.

MRI assessment of the effects of acetazolamide and external lumbar drainage in idiopathic Normal Pressure Hydrocephalus

“…It is noteworthy that the patient with the highest volume of drained CSF also had the greatest reduction in ventricle size (patient ELD_3 in Table 3 ), but there was no clear association between ventricle volume change and the amount of drained CSF or symptomatic response. This is consistent with previously reports that change in ventricular volume does not correlate with outcome of iNPH treatment [ 23 ] or the amount of drained CSF [ 24 , 25 ].…”

“…There was an intriguing correlation between MD change within post-intervention T1-hypointensities and the volume of the CSF drained during ELD (Figure 3 ), but further study and more patients are needed to clarify the relationship between ELD and change in interstitial water. We expect that the time-interval between the end of ELD and the follow-up MRI scan is an important covariate, similarly to volumetric changes following CSF removal [ 25 ].

Figure 2 Illustration of DW-MRI changes location.

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Aqueductal Stroke Volume: Comparisons with Intracranial Pressure Scores in Idiopathic Normal Pressure Hydrocephalus

“…As pointed out by Chiang et al, 33 it seems reasonable that the aqueduct can adapt to increased flow, similar to the ad- aptation of the blood vessel lumen area to maintain a wall shear stress within a normal range. 37 ASV and ventricular volume declined after shunting; this change is consistent with that in previous studies, 14,38 while aqueductal area did not change. While ASV did not reflect the clinical severity of iNPH preshunting and did not compare with any pressure parameters, reduced ASV after shunting might therefore be primarily influenced by reduced ventricular size, rather than reflecting a clinical response, contrary to what has been suggested previously.…”

Automated Quantitation of Spinal CSF Volume and Measurement of Craniospinal CSF Redistribution following Lumbar Withdrawal in Idiopathic Intracranial Hypertension

“…A small reduction of 1.4% in ventricular volume was reported following high-volume CSF withdrawal in elderly patients with normal pressure hydrocephalus. 2 In contrast, in our study of younger patients with IIH, the ventricular volume was unchanged following CSF withdrawal. This finding can be partly attributed to the much smaller ventricular volume (16.2 versus 160 mL) and the smaller amount of CSF removed (15.8 versus 35 mL) in the current study.…”