Ectopic cerebellum in the posterior cranial fossa

Isolated, well-differentiated ectopic cerebellar tissue is extremely rare, with only eight cases in the literature. We describe a unique case of histopathologically proven ectopic cerebellar tissue presenting as a discrete extra-axial mass in the posterior cranial fossa. We describe the clinical, CT and MRI findings, as well as the surgical and histopathological findings and review the relevant literature.     

Severe cerebellar mutism after posterior fossa tumor resection

Cerebellar mutism is an infrequent but important complication after posterior fossa surgery in children. Dysarthria, irritability and ataxia are among the signs and symptoms of this disorder, which are usually mild and self-limiting. However, in severe cases, there can be impairment of higher-level cognitive functions, affecting the child's future personal and social relations. This disorder has been described in many other situations and consequently pediatricians should be familiar with its symptoms, physiopathology, diagnosis, degrees of severity, treatment, and prognosis, since a multidisciplinary approach is required. We present the case of a 5-year-old boy who underwent surgery for a low-grade ependymoma in the fourth ventricle; 48 hours after surgical resection, the boy developed irritability, cranial nerve involvement and stereotyped movements in the context of active hydrocephalus. His symptoms progressively improved 6 weeks after the intervention. We review the literature on cerebellar mutism and discuss the physiopathology of this disorder, which seems to confirm that the cerebellum not only acts as a simple coordinator of motor function, but also plays an important role in higher-level cognitive functions, such as language.     

Hypothalamo-pituitary-adrenal axis integrity after cranial irradiation for childhood posterior fossa tumours

BACKGROUND: The evolution of anterior pituitary deficits after treatment for pituitary tumours has been largely attributed to local irradiation, but may be influenced as much by tumour mass or surgery. Other than growth hormone (GH) insufficiency, the late endocrinopathies after survival from non-central brain tumours have been little documented. The aim of this study was to investigate the hypothalamic-pituitary-adrenal (HPA) axis in long-term survivors of cranial irradiation for childhood posterior fossa tumours. PROCEDURE: We studied long-term data in patients treated prepubertally for posterior fossa brain tumours and systematically referred by radiation oncologists for growth and pubertal monitoring to the London Centre for Paediatric Endocrinology over the last 25 years. They must have undergone HPA axis assessment twice, first prepubertally at documentation of growth failure, and second at completion of growth and puberty. Data on sixteen patients (12 males, 4 females; median age: 5.7 years, range: 2.5-8.8 years), who had undergone excision surgery with high dose cranial irradiation and/or chemotherapy for childhood posterior fossa tumours, were examined. Patients were followed for a median of 11.0 (range: 6.8-21.4) years after radiotherapy. HPA axis assessment was undertaken with the insulin-induced hypoglycaemia test (ITT). Basal thyroid, cortisol and gonadal function tests were undertaken annually throughout the follow-up period and any deficits replaced. RESULTS: At each ITT, all patients mounted an inadequate GH response. By the end of the follow-up period all patients remained severely GH deficient, two (12.5%) had partial ACTH insufficiency, one (6.3%) had secondary hypothyroidism but none were gonadotropin deficient or hyperprolactinaemic. CONCLUSIONS: Unlike the severe, evolving multiple pituitary deficits after treatment of pituitary or central tumours in adults, these findings in children with posterior fossa tumours suggest that, with the exception of GH, neurotoxicity due to irradiation per se is associated with a low prevalence of anterior pituitary hormone deficiencies, even at a long follow-up. Since the children in this study were selected for assessment on the basis of growth failure, the high prevalence of GH insufficiency at first testing is to be expected; however, the early onset (within 1-3 years of irradiation) and permanence we have identified supports the view that GH is the most sensitive hormone to radiation injury.     

Transient eye closure after posterior fossa tumor surgery in children.

Transient cerebellar eye closure following posterior fossa tumor surgery in children has recently been observed. This phenomenon is characterized by a transient inability to open the eyes postoperatively with complete resolution within 4-6 days. Presented are four cases of transient cerebellar eye closure after posterior fossa tumor surgery in children. Possible mechanisms are reviewed with regard to historical works of cerebellar stimulation in man, and anatomical structures and pathways which might be involved.     

Ultrasonic measurements of the posterior cranial fossa structures in neonates and infants

The structures in the posterior cranial fossa of neonates and infants were visualized ultrasonically via the anterior fontanelle. The diamters of the cerebellar vermis, pons, fourth ventricle and cisterna vermis were measured in the midsagittal plane in neonates (n=76), 1-month-old infants (n=61) and 3-to-6-month-old infants (n=35). The normal values obtained will be useful for evaluation of morphological abnormalities in the posterior cranial fossa.     

Cerebellar mutism after posterior fossa surgery

A large midline posterior fossa medulluloblastoma and a cerebellar arteriovenous malformation with associated clot were moved with postoperative mutism. Mutism was immediate and resolved into an ataxic dysarthria with residual mild dysarthria at 3 months. The literature is reviewed, and the clinicopathological and neurophysiological data of cerebellar function in speech are discussed. Acute injury to the midportion of the cerebellum with or without dentate nuclear involvement can cause a spectrum of speech disturbances. The more widespread the injury to the midportion of the cerebellum with dentate nuclei involvement the greater the risk of developing postoperative mutism.     

小儿后颅窝肿瘤的临床特点与误诊分析

目的探讨小儿后颅窝肿瘤的临床特点及误诊原因。方法回顾性分析63例小儿后颅窝肿瘤的临床症状、体征和影像学表现。结果本组主要症状和体征为头痛、呕吐、步态不稳、颈强直、躯体共济失调和头围异常增大,其中25例误诊为病毒性脑炎,16例误诊为急性脑脊髓膜炎,12例误诊为急性胃肠炎。CT检查阳性率为96.8%,MRI阳性率为100%,MRI定性诊断准确率为85.7%。结论小儿后颅窝肿瘤临床症状不典型,早期体征不明显,采取有效的影像学检查措施有助于减少或避免误诊。     

Cardiorespiratory fitness in survivors of pediatric posterior fossa tumor

Advances in medical therapies have greatly improved survivorship rates in children diagnosed with brain tumor; as a result, morbidities associated with survivorship have become increasingly important to identify and address. In general, pediatric posterior fossa tumor survivors tend to be less physically active than peers. This may be related to late effects of diagnosis and treatment, including cardiovascular, endocrine, psychological, and neurocognitive difficulties. Exercise has been shown to be effective in improving physical functioning, mood, and even cognitive functioning. Consequently, the benefits of physical exercise need to be explored and incorporated into the daily lives of pediatric posterior fossa tumor survivors. The primary aim of the present study was to establish the feasibility and safety of cardiorespiratory fitness testing in pediatric posterior fossa tumor survivors who had received cranial radiation therapy. In addition, comparing our cohort with previously published data, we found that pediatric posterior fossa tumor survivors tended to be less fit than children with pulmonary disease and healthy controls and approximately as fit as children with chronic heart disease and survivors of other types of childhood cancer. The importance of cardiorespiratory fitness in pediatric posterior fossa tumor survivors is discussed along with implications for future directions.     

Prenatal imaging of posterior fossa disorders. A review

With advances in fetal imaging, prenatal diagnosis of posterior fossa anomalies has been greatly improved. Based on the anatomical approach proposed by Guibaud and Desportes in 2006, the main anomalies depicted according to the algorithm includes: (1) increased “fluid-filled” space of the posterior fossa, (2) abnormal biometry of the cerebellum, and (3) abnormal cerebellar anatomy. In this review, the spectrum of PF anomalies is covered in an attempt to update this approach in the light of both our experience, more than a decade since this algorithm was published, and the latest data in the literature.     

Posterior fossa measurements II. Size of the posterior fossa in myelomeningocele

In seven myelomeningocele patients, six were operated upon while in one severe case no surgery was performed. The posterior fossa areas were measured and expressed by the posterior fossa ratio method. In two shunted patients both ratios were primarily below the lowest normal limit, but following shunt operation the ratios become normal. In five patients who were not shunted one only showed a normal ratio, two showed borderline values and in a fourth instance the ratio normalized but before two years had passed. The fifth case remained unoperated and therefore the natural course could be followed. In this case the decrease in the posterior fossa ratio explained the progress of hydrocephalus.     

Posterior fossa measurements I. The normal size of the posterior fossa

The posterior fossa area was defined as that situated below Twining's line while the one above was called the supratentorial area. A ratio has been calculated: Above 7 years this was (mean) 16.5%±2 and below 7 years 14.0%±4, with the ranges (13.2–20.2) and (9.0–19.4), respectively. When the ratio falls below 13% and 9% respectively, this implies therefore a malformation of the posterior fossa, i. e. too flat a space. Two formulas for calculation of the areas mentioned as well as two other ratios are also introduced.