Evaluation of hydrocephalus and other cerebrospinal fluid disorders with MRI: An update

Insights Imaging (2014) 5:531–541 DOI 10.1007/s13244-014-0333-5 PICTORIAL REVIEW Evaluation of hydrocephalus and other cerebrospinal fluid disorders with MRI: An update Merve Gulbiz Kartal & Oktay Algin Received: 12 October 2013 / Revised: 8 April 2014 / Accepted: 15 April 2014 / Published online: 6 June 2014 # The Author(s) 2014. This article is published with open access at Springerlink.com Abstract MRI is not only beneficial in the diagnosis of cerebrospinal fluid (CSF)-related diseases, but also aids in planning the management and post-surgery follow-up of the patients. With recent advances in MRI systems, there are many newly developed sequences and techniques that rapidly enable evaluation of CSF-related disorders with greater accuracy. For a better assessment of this group of disorders, radiologists should follow the developments closely and should be able to apply them when necessary. In this pictorial review, the role of MRI in the evaluation of hydrocephalus, CSF diversion techniques, and other CSF disorders is illustrated. Teaching Points • The 3D-SPACE seems to be most efficient technique for evaluation of hydrocephalus and ventriculostomy. • In complex cases, PC-MRI, 3D-heavily T2W, and/or CEMRC images may prevent false results of 3D-SPACE. • MRI is beneficial in the diagnosis and management of hydrocephalus and other CSF-related diseases. Keywords MRI . Hydrocephalus . CSF . 3D-SPACE . Endoscopic third ventriculostomy . Ventriculoperitoneal shunt Introduction Progressive developments in magnetic resonance imaging (MRI) technologies allow us to better assess CSF circulation. Therefore, MRI aids in the diagnosis of M. G. Kartal (*) : O. Algin Department of Radiology, Ataturk Training and Research Hospital, 06050 Bilkent, Ankara, Turkey e-mail: O. Algin e-mail: diseases that result from alterations of the CSF circulation. Hydrocephalus, which constitutes a major CSFrelated disorder, is well demonstrated using MRI. MRI also helps to discriminate the aetiology of the disease [1]. The provided data are important for planning the management as well as follow-up of the patients. MRI is also effective in the diagnosis and treatment planning of other CSF disorders such as CSF leakage, arachnoid cysts, etc. [2–4]. In this review, the role of MRI in the evaluation of hydrocephalus and other CSF disorders with emphasis on the most recently used sequences in routine practice is covered. CSF circulation The CSF volume is approximately 150 ml in adults; 125 ml is distributed in the cranial and spinal subarachnoid spaces and 25 ml is found in the ventricles [1]. A volume of 400–500 ml is secreted and approximately 330–380 ml of CSF enters the venous circulation daily [2]. CSF is produced in the choroid plexus, brain parenchyma, spinal cord, and ependymal lining of the ventricles. Most is secreted in the lateral ventricles and leaves the ventricles through the foramen of Monro to enter the third ventricle. From there, the CSF flows into the fourth ventricle through the aqueduct. It leaves the fourth ventricle by the foramen of Magendie and foramina of Luschka and enters the subarachnoid space. Cerebrospinal fluid is essentially absorbed into the internal jugular system via cranial arachnoid granulations. However, multiple experiments indicate that movement along nerve roots and exiting vessels also plays a role [1, 3]. In addition, absorption towards the interstitial compartment occurs via the Virchow-Robin spaces [1]. 532 Hydrocephalus Hydrocephalus is a complex disorder that can develop for various reasons. Dilatation of the ventricular system may lead to loss of brain cells resulting in a variety of neurological symptoms, stroke, and sometimes even death due to pressure applied on the brain parenchyma [4]. The causes of CSF increase are often obstructive diseases such as cystic lesions, tumours or obstructive membranes [5–7]. Rarely, it may be the result of excessive CSF production, which may be due to pathologies at the sites where CSF production takes place. More frequently, it is be due to an obstruction in the ventricular system (obstructive or non-communicating type) or interrupted CSF absorption or flow (communicating type) [8]. In young adults and children, obstructive-type hydrocephalus is the most common type [6, 9, 10]. In some instances, such as meningitis, both absorption and flow may be interrupted, which is defined as complex-type hydrocephalus [11]. Although there are several theories regarding the pathophysiology of hydrocephalus, recently the most widely accepted one has been Greitz’s hyperdynamic flow theory, which divides hydrocephalus into two main groups, acute and hydrocephalus [8]. Acute hydrocephalus is caused by an intraventricular CSF obstruction. Chronic hydrocephalus is further divided into communicating and chronic obstructive hydrocephalus. The theory proposes that chronic hydrocephalus is a result of decreased intracranial capillaries, which causes restricted arterial pulsations and increased capillary pulsations and decreased intracranial compliance [8, 9]. The most commonly used radiological criteria in the diagnosis of hydrocephalus are given below [12, 13] (Figs. 1 and 2); 1. Ventriculomegaly (Evans' index >0.3), 2. Enlargement of the third ventricular recesses and lateral ventricular horns, 3. Decreased mamillopontine distance and frontal horn angle, 4. Thinning and elevation of the corpus callosum, 5. Normal or narrowed cortical sulci, 6. Periventricular white matter hyperintensities (interstitial oedema and acute hydrocephalus), 7. Aqueductal flow void phenomenon in T2W images (a sign of communicating hydrocephalus). These criteria are not specific for hydrocephalus, and their sensitivities are poor [13]. The gold standard diagnostic method for hydrocephalus is ventriculographic studies [6]. On the other hand, this is a highly invasive method and may lead to serious complications. Therefore, new MRI techniques have been developed in order to determine the aetiology and treatment. These techniques include phase-contrast MRI (PC-MRI), three-dimensional (3D) heavily T2W sequences and contrastmaterial-enhanced MR cisternography (CE-MRC) [14, 15]. All three techniques have their own advantages and disadvantages. Insights Imaging (2014) 5:531–541 PC-MRI provides quantitative and qualitative data regarding CSF circulation. On the other hand, in the presence of complex or turbulent flow, results may be false positive or negative [14, 15]. Another drawback of the technique is that it is extremely sensitive to technical factors [16]; 3D heavily T2W sequences [such as 3D-DRIVE (Philips), 3D-CISS (Siemens) or FIESTA-C (GE)] may provide accurate anatomical data. However, these techniques lack physiological information [5–7]. CE-MRC is an invasive test and is highly dependent on radiologist experience [6]. In recent years, 3D sampling perfection with applicationoptimised contrast using the variable flip-angle evolution (3DSPACE) te (...truncated)