ΔADC in Idiopathic Normal Pressure Hydrocephalus After Shunt Surgery

Ryoko Yamamori¹, Tosiaki Miyati¹, Naoki Ohno¹, Mitsuhito Mase², Tomoshi Osawa², Shota Ishida¹, Hiroto Kan³, Nobuyuki Arai³, Harumasa Kasai³, and Yuta Shibamoto³

¹Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan, ²Department of Neurosurgery, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan, ³Department of Radiology, Nagoya City University Hospital, Nagoya, Japan

Synopsis

Apparent diffusion coefficient (ADC) in brain significantly changed during the cardiac cycle, and this change (ΔADC) in patients with idiopathic normal pressure hydrocephalus (iNPH) characterized by low intracranial compliance was significantly higher than those in control subjects. Shunt surgery is the most common treatment for iNPH. In this study, we determined and compared ΔADC values of the white matter in iNPH before and after shunt surgery. ΔADC in the frontal white matter decreases with the shunt surgery. ΔADC analysis makes it possible to noninvasively provide detailed information on change in the intracranial condition due to the shunt surgery.

INTRODUCTION

We have reported that the apparent diffusion coefficient (ADC) in brain significantly changed during the cardiac cycle, and this change (ΔADC) in the frontal white matter in patients with idiopathic normal pressure hydrocephalus (iNPH) characterized by low intracranial compliance was significantly higher than those in patients with atrophic ventricular dilatation and control subjects [1]. Shunt surgery by which the reduced intracranial compliance can be improved is the most common treatment for iNPH [2]. In this study, we assessed the ΔADC of the white matter in iNPH before and after shunt surgery.

MATERIALS AND METHODS

With a 1.5-T MR imaging unit (Gyroscan Intera; Philips Medical Systems, Best, The Netherlands), ECG-triggered single-shot diffusion echo-planar imaging (b = 0 and 1000 s/mm²) was used with sensitivity encoding and half-scan techniques to minimize the bulk motion. The imaging parameters were set at TR, two R-R intervals; TE, 70 msec; flip angle, 90 degrees; section thickness, 4 mm; imaging matrix, 64x64; field of view, 256 mm; number of signals averaged, two; the number of cardiac phases, 20; duration and respective times between leading edges of the diffusion gradients, 28.6 and 48.7 msec. Then, we determined the maximum change in ADC (ΔADC) during the cardiac cycle and compared those values of the white matter in patients with iNPH before and after shunt surgery (n = 7, all patients improved symptoms after the shunt procedure, ie., definite iNPH). This study was approved by the institutional review board.

RESULTS AND DISCUSSION

ΔADC in the frontal white matter in iNPH after the shunt surgery was significantly lower than that before shunt surgery (Fig. 1), indicating that fluctuation of water molecules in the white matter caused by the arterial inflow, ie., volume loading of the brain as the driving force was reduced by increase in the intracranial compliance after the shunt. However, there was no significant difference in ADC values in iNPH before and after shunt surgery (Fig. 2).

CONCLUSION

ΔADC in the frontal white matter decreases with the shunt surgery. ΔADC analysis makes it possible to noninvasively provide detailed information on change in the intracranial condition due to the shunt surgery.

Acknowledgements

No acknowledgement found.

References

[1] Ohno N, et al., Radiology. 2011; 261: 560-5.
[2] Eide PK, et al., Acta Neurochir (Wien). 2008; 150: 1141-7.

Figures

(a)

(b)
Fig. 1 (a) ΔADC values and (b) typical examples before and after shunt surgery.

Fig. 2 ADC values before and after shunt surgery.

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)

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