Neurenteric cyst of the lower clivus.

OBJECTIVE: Neurenteric cysts (NCs) typically arise as benign ventral intradural extramedullary developmental malformations of the spine which contain heterotopic epithelium resembling the intestinal or respiratory tracts. Intracerebral NCs are extremely rare, though the frequency of symptomatic reports and incidental findings is increasing, perhaps because of advances in neuroimaging. Recognition of the unique radiographic and histopathologic features of this entity is of growing importance in the treatment of cysts of the neural axis. We present an unusual case of an NC arising at the lower clivus. CLINICAL PRESENTATION: A 58-year-old man presented with occipitalgia, diplopia, a bilateral hearing deficit, and mild dysphagia. Computed tomography and magnetic resonance imaging demonstrated a 5 x 2 x 3-cm extra-axial cystic midline mass anterior to the brainstem at the lower clivus with posterior cyst wall enhancement. INTERVENTION: The patient underwent a left lateral suboccipital total macroscopic resection of the lesion. Microscopic examination and histopathologic findings were consistent with a diagnosis of NC. CONCLUSION: We describe the clinical presentation, imaging, and histopathologic characteristics, and discuss the diagnosis and surgical treatment of this rare lesion and related pathologic entities. Because of the remote possibility of delayed recurrence, even in cases of apparent total cyst wall removal, long-term serial imaging and a consideration of reoperation for recurrences is advisable.

[Percutaneous vertebroplasty for vertebral compression fracture].

BACKGROUND: Percutaneous vertebroplasty has become an option for the treatment of painful osteoporotic compression fractures in patients in whom conservative medical management has failed. AIM: This paper assessed the effectiveness and safety of percutaneous vertebroplasty in patients with focal pain caused by compression vertebral body fractures. MATERIALS AND METHODS: Over a twenty-five-month period 63 patients underwent percutaneous vertebroplasty, and ten of these patients were subsequently retreated, for a total of 73 operations on 93 vertebrae. The patients were affected by osteoporotic compression fractures (n=57) or by benign or malignant infiltrative processes (n=6). All patients were examined at discharge and thereafter to assess the level of pain and investigate possible changes in the quality of life. The mean length of follow-up was 15.2 months. RESULTS: After treatment, almost 90% of patients reported complete disappearance or significant alleviation of the pain. In 7 of 63 of the patient (11%) there were small asymptomatic leakages of cement outside the vertebral body. A substantial number of patients with osteoporosis, 19% of the study population, experienced new fractures following treatment with vertebroplasty. DISCUSSION: Our experience confirms the effectiveness of vertebroplasty to pain caused by vertebral fractures. If the indications are strictly followed, improvement of symptoms is often immediate, allowing the return of mobility, and patient satisfaction with surgery is higher. The use of appropriate systems limits the number of complications.

Instability of the apo form of aromatic L-amino acid decarboxylase in vivo and in vitro: implications for the involvement of the flexible loop that covers the active site.

Pyridoxine deficiency caused a decrease in the amount of aromatic L-amino acid decarboxylase (AADC) in PC12 cells to less than 5% of the control. The degree of the enzyme saturation with the coenzyme pyridoxal 5'-phosphate (PLP) was around 90% for both the control and the pyridoxine-deficient cells, contrary to earlier reports by others. Mathematical analysis of the result indicated that the AADC apoenzyme is degraded at least 20-fold faster than the holoenzyme in the cells. To determine the mechanism of the preferential degradation of the apoenzyme, in vitro model studies were carried out. AADC has a flexible loop that covers the active site. This loop was easily leaved by proteases at similar rates for both the holoenzyme and the apoenzyme. However, in the presence of the substrate analog, dopa methyl ester, the holoenzyme was not cleaved by proteases, while the apoenzyme was cleaved similarly. These results indicated that the ligand that forms a Schiff base (aldimine) with PLP is fixed to the active site and stabilizes the flexible loop. The structure of the rat AADC-dopa complex modeled on the crystal structure of pig AADC showed that the flexible loop can fit in the concave surface at the entrance of the active site, its aliphatic and aromatic residues forming hydrophobic interactions with the substrate catechol ring. It was postulated that the flexible loop of the holoenzyme is stabilized in vivo by taking a closed structure that holds the PLP-substrate aldimine, while the apoenzyme cannot bind the substrate and its flexible loop is easily cleaved, leading to the preferential degradation of the apoenzyme.