Cerebellar mutism syndrome (CMS), also known as posterior fossa syndrome, is encountered in a subset of children who have undergone an operative procedure of the posterior cranial fossa, mainly involving the vermis, and the most frequent underlying pathology is proved to be medulloblastoma. The most common characteristics of this syndrome include an often transient, although protracted, language impairment, emotional lability, along with cerebellar, and brainstem dysfunction. Nevertheless, a significant number of patients experience persistent neurological deficits and lasting neurocognitive impairment. A lot of research and clinical studies have been performed in order to better delineate this syndrome. The main obstacles in our way to highlight all aspects of this syndrome were related with an inconsistent nomenclature, poorly defined diagnostic criteria, and uncertainty surrounding risk factors and etiology. Currently, there is a combination of diagnostic criteria that are regarded as prerequisites in order to establish the diagnosis of CMS. These include language impairment and emotional lability, as proposed by the international Board of the Posterior Fossa Society in their consensus statement. Several risk factors are recognized as implicated in the pathogenesis of this syndrome, including midline tumor location, diagnosis of medulloblastoma, younger age at diagnosis, and preoperatively established language impairment. A proposed etiology of CMS includes disruption of the cerebellar outflow tracts, the cerebellar nuclei, and their efferent projections through the superior cerebellar peduncle. Specific treatment for CMS is lacking, and it continues to be directed at symptom management. Our aim is to present a comprehensive narrative review of CMS etiology, diagnosis, risk factors, clinical presentation, and clinical management. Moreover, we attempt to recognize the most widely recognized priorities of the research community in order to expand our knowledge in the era of diagnostics, prevention, and therapeutic options for patients suffering from CM, or who are at risk for development of this syndrome.

The introduction of ventricular shunts dramatically changed the outcome and quality of life of hydrocephalic patients. However, shunt surgery continues to be associated with numerous adverse events. Headache is one of the most common complications after shunt operation. It is often over a prolonged duration, the symptoms resemble migraine, and pain does not respond to medication. We propose invasive peripheral nerve stimulation as a possible solution in the treatment of patients suffering from chronic headache associated with shunted hydrocephalus. A young woman with daily holocephalic headache with diffuse pain exacerbated by lying down. Imaging revealed panventricular enlargement and possible stenosis of the aqueduct. When a ventriculoperitoneal shunt was placed, clinical symptoms resolved. Nevertheless, she gradually exacerbated after a second valve replacement due to wound infection. Imaging revealed decompressed ventricles and appropriate shunt placement. The diagnosis of chronic post-intracranial disorder headache was set. Therefore, occipital nerve stimulation was applied and considering that the patient had not a total response, bilateral parietal stimulation was added. Three months after the combined PNS she experienced total remission of headache. Combined PNS eases refractory headaches much more than occipital nerve stimulation alone and could be considered as a solution for shunted hydrocephalus associated headache.

The pathophysiologic substrate of pediatric hydrocephalus has not been thoroughly explained. Because of that, the available treatment options and protocols will be largely based on expert opinions or the results of single-center databases, until a more comprehensive knowledge of the various subcategories of hydrocephalus is undertaken. In retrospect, we mention that valve-based shunt systems have been constituting the mainstay of therapy since the late 1950s. The initially used shunt systems were concerning the ventricular system and the atrium. In the 1970s, VA shunts were not the main stay of treatment, as the primary location for the distal end was substituted by the peritoneum, due to the emergence of the ventriculoperitoneal shunts. Several types of one-way valve-based shunt systems have been developed. The ultimate goal was the drainage of the appropriate amount of CSF, in order to avoid either overdrainage or underdrainage, without interfering with normal brain development or cognition. Our review briefly analyzes these valve types and attempts a comparison, based on their functional characteristics. In addition to the peritoneum, other distal locations for shunt placement have been explored, including the pleural space and gallbladder. A separate subcategory includes the shunt systems which incorporate the lumbar subarachnoid space as the proximal location for the central catheter. Nowadays, the only available surgical alternative for the treatment of hydrocephalus is ETV. Since 2000, approximately 50% of children suffering hydrocephalus have been considered to be candidates for the execution of ETV. The potential benefits are that it closely resembles to the normal, physiological pathway of CSF absorption, thus circumventing the need for an artificial shunt system. Moreover, this technique is associated with lower infection rates, as well as on average, with a lower reoperation rate. Attempts of future progression are largely based on the development of improved shunt valve systems that could be affordable worldwide, as well as with the constant availability of ETV in developing countries. Another term that deserves special mention is related with the outcome of ETV in children who had a medical history of previously incorporated shunts and who were subsequently experiencing shunt dysfunction. This subset of patients is discussed in terms of efficacy (success rate from 40% to 80%) and safety (0%–32.5% of complications). Based on literature reviews, well-recognized predictive factors associated with secondary ETV failure include age, early onset of hydrocephalus, and prematurity. Currently, there is no consensus when the optimum surgical strategy is concerned in the different subgroups of patients, who are suffering from shunt dysfunction. Therefore, another issue that this review attempts to elucidate is the identification of subgroups of patients in whom shunt treatment is associated with a favorable outcome, compared to ETV, and vice versa. The objective of our study is to evaluate the comparative safety and efficacy, as well as the outcomes, of shunting and ETV in pediatric hydrocephalus cases. Anatomic and molecular substrate of hydrocephalus need to be better elucidated, so that medications or genetic modifications become more effective in order to offer a potential cure for hydrocephalus. Advancements in the treatment of hydrocephalus will depend on research into the shared molecular mechanism underlying various forms of the condition, paving the way for new therapeutic strategies.

The ultimate goal of our review is to draw clinician’s attention, especially of those who are managing pediatric patients with permanent, long-standing, ventriculoperitoneal or, less commonly, ventriculo-atrial shunts. This specific subgroup of patients may eventually suffer from severe, intractable headaches which may negatively impair their quality of daily living. In the absence of any other clinical condition that could be attributed as the cause of the headache, shunt overdrainage should not be overlooked but, on the contrary, should be seriously taken into consideration in the therapeutic armamentarium of such cases, that are difficult to be handled.