Conceptual design of a GEM (gas electron multiplier) based gas Cherenkov detector for measurement of 17 MeV gamma rays from T(D, γ)5He in magnetic confinement fusion plasmas.

The only method for assessing the fusion power throughput of a deuterium-tritium (DT) reactor presently relies on determining the absolute number of 14 MeV neutrons produced in the DT plasma. An independent method, developed and investigated during the recent DT campaign at the Joint European Torus, is based on the absolute counting of 17 MeV gamma rays produced by the competing T(D, γ)5He reaction that features a very weak branching ratio (about 3-6 × 10-6) when compared to the main T(D, n)4He reaction. The state-of-the-art spectrometer used for gamma-ray measurements in magnetic confinement fusion plasmas is LaBr3(Ce) scintillator detectors, although they require significant neutron shielding to extract a relatively weak gamma-ray signal from a much more abundant neutron field. A better approach relies on a gamma-ray detector that is intrinsically insensitive to neutrons. We have advanced the design of a gamma-ray counter based on the Cherenkov effect for gamma-rays whose energy exceeds 11 MeV, optimized to work in the neutron-rich environment of a steady-state, magnetically confined fusion plasma device. The gamma-rays interact with an aluminum window and extract electrons that move into the radiator emitting photons via the Cherenkov effect. Since the Cherenkov light consists of few photons (25 on average) in the far UV band (100-200 nm), a pre-amplifier is required to transport the photons to the neutron-shielded location, which may be a few meters away, where the readout elements of the detector, either a silicon or standard photomultiplier tube, are placed. The present work focuses on the development of a scintillating GEM (Gas Electron Multiplier) based pre-amplifier that acts as a Cherenkov photon pre-amplifier and wavelength shifter. This paper presents the result of a set of Garfield++ simulations developed to find the optimal GEM working parameters. A photon gain of 100 is obtained by biasing a single GEM foil to 1 kV.

Does Phase-Contrast Imaging through the Cerebral Aqueduct Predict the Outcome of Lumbar CSF Drainage or Shunt Surgery in Patients with Suspected Adult Hydrocephalus?

BACKGROUND AND PURPOSE: Radiologic imaging plays a key role in diagnosing chronic adult hydrocephalus, but its role in predicting prognosis is still controversial. We sought to evaluate the effectiveness of cardiac-gated phase-contrast MR imaging through the cerebral aqueduct in predicting the clinical response to diagnostic lumbar puncture/lumbar drainage and shunt surgery in suspected adult hydrocephalus. MATERIALS AND METHODS: In this retrospective study, the phase-contrast MR imaging of 185 patients with suspected chronic adult hydrocephalus was evaluated using the CSF Flow software package. Decision-making for shunt placement was performed in this cohort on the basis of clinical assessment alone without the availability of quantitative phase-contrast MR imaging results. We recorded the response to lumbar puncture or lumbar drainage and shunt surgery using quantitative tests such as the Tinetti Test, the Timed Up and Go, and the Mini-Mental State Examination and qualitative measures of gait, urinary, and cognitive symptom improvement before and after lumbar puncture/lumbar drainage and shunt surgery. Quantitative analysis of phase-contrast MR imaging was compared with clinical outcome measures. RESULTS: Both CSF stroke volume and flow rate overlapped between lumbar puncture/lumbar drainage responders and nonresponders. There was also a significant overlap between shunt responders and nonresponders. Aqueductal stroke volume or flow rate alone was a poor predictor of lumbar puncture/lumbar drainage and shunt surgery response. Quantitative clinical measures after lumbar puncture/lumbar drainage were better predictors of shunt response. CONCLUSIONS: This study suggests that the results of phase-contrast MR imaging through the cerebral aqueduct alone should not be used to select patients for diagnostic or therapeutic CSF diversion.

3D quantitative assessment of response to fractionated stereotactic radiotherapy and single-session stereotactic radiosurgery of vestibular schwannoma.

OBJECTIVES: To determine clinical outcome of patients with vestibular schwannoma (VS) after treatment with fractionated stereotactic radiotherapy (FSRT) and single-session stereotactic radiosurgery (SRS) by using 3D quantitative response assessment on MRI. MATERIALS: This retrospective analysis included 162 patients who underwent radiation therapy for sporadic VS. Measurements on T1-weighted contrast-enhanced MRI (in 2-year post-therapy intervals: 0-2, 2-4, 4-6, 6-8, 8-10, 10-12 years) were taken for total tumour volume (TTV) and enhancing tumour volume (ETV) based on a semi-automated technique. Patients were considered non-responders (NRs) if they required subsequent microsurgical resection or developed radiological progression and tumour-related symptoms. RESULTS: Median follow-up was 4.1 years (range: 0.4-12.0). TTV and ETV decreased for both the FSRT and SRS groups. However, only the FSRT group achieved significant tumour shrinkage (p < 0.015 for TTV, p < 0.005 for ETV over time). The 11 NRs showed proportionally greater TTV (median TTV pre-treatment: 0.61 cm(3), 8-10 years after: 1.77 cm(3)) and ETV despite radiation therapy compared to responders (median TTV pre-treatment: 1.06 cm(3); 10-12 years after: 0.81 cm(3); p = 0.001). CONCLUSION: 3D quantification of VS showed a significant decrease in TTV and ETV on FSRT-treated patients only. NR had significantly greater TTV and ETV over time. KEY POINTS: Only FSRT not GK-treated patients showed significant tumour shrinkage over time. Clinical non-responders showed significantly less tumour shrinkage when compared to responders. 3D volumetric assessment of vestibular schwannoma shows advantages over unidimensional techniques.

Normal pressure hydrocephalus: long-term outcome after shunt surgery.

BACKGROUND/OBJECTIVE: Little is known about the long-term clinical course and management of patients with normal pressure hydrocephalus (NPH) treated by cerebrospinal fluid (CSF) shunting. METHODS: We retrospectively reviewed records of 55 patients diagnosed with idiopathic NPH (INPH) and treated with CSF shunts, all of whom were followed for more than 3 years after the original shunt surgery. At each annual follow-up visit, the patient was assessed by Folstein Mini Mental State Examination, detailed clinical evaluation of gait and assessment of headache, cognition, gait or urination, as assessed by the patient and relatives. RESULTS: The mean duration of follow-up was 5.9+/-2.5 years. There was an overall sustained improvement among all symptoms. Gait showed the highest maintenance of improvement over baseline (83% at 3 years and 87% at the last analysed follow-up of 7 years), cognition showed intermediary improvement (84% and 86%, respectively), and urinary incontinence showed the least improvement (84% and 80%, respectively). Fifty-three percent of patients required shunt revisions. Indications for revision included shunt malfunction (87%), infection (10%) and change of shunt configuration (3%). Overall, 74% revisions resulted in clinical improvement. CONCLUSIONS: Clinical improvement of patients with NPH can be sustained for 5-7 years in some patients with NPH, even if shunt revision surgery is needed multiple times. With earlier diagnosis and treatment of NPH and the increasing lifespan of the ageing population, the need for long-term follow-up after shunt surgery for NPH may be greater than it was in the past. Monitoring, identification and treatment of shunt obstruction is a key management principle.

Utility of CSF pressure monitoring to identify idiopathic intracranial hypertension without papilledema in patients with chronic daily headache.

The aim of the present study was to report on the utility of continuous Pcsf monitoring in establishing the diagnosis of idiopathic intracranial hypertension without papilledema (IIHWOP) in chronic daily headache (CDH) patients. We report a series of patients (n = 10) with refractory headaches and suspected IIHWOP referred to us for continuous Pcsf monitoring between 1991 and 2000. Pcsf was measured via a lumbar catheter and analysed for mean, peak, highest pulse amplitude and abnormal waveforms. A 1-2 day trial of continuous controlled CSF drainage (10 cc/ h) followed Pcsf monitoring. Response to CSF drainage was defined as improvement in headache symptoms. Patients with abnormal waveforms underwent a ventriculoperitoneal (VPS) or lumboperitoneal (LPS) shunt insertion. All patients had normal resting Pcsf (8 +/- 1 mmHg) defined as ICP < 15 mmHg. During sleep, all patients had B-waves and 90% had plateau waves or near plateau waves. All patients underwent either a VPS or LPS procedure. All reported improvement of their headache after surgery. Demonstration of pathological Pcsf patterns by continuous Pcsf monitoring was essential in confirming the diagnosis of IIHWOP, and provided objective evidence to support the decision for shunt surgery. Increased Pcsf was seen mostly during sleep and was intermittent, suggesting that Pcsf elevation may be missed by a single spot-check LP measurement. The similarity between IIHWOP and CDH suggests that continuous Pcsf monitoring in CDH patients may have an important diagnostic role that should be further investigated.

Interaction between krit1 and icap1alpha infers perturbation of integrin beta1-mediated angiogenesis in the pathogenesis of cerebral cavernous malformation.

Cerebral cavernous malformation (CCM) is a common autosomal dominant disorder characterized by venous sinusoids that predispose to intracranial hemorrhage. CCM is genetically heterogeneous, with loci at 7q, 7p and 3q. Mutations in KRIT1 account for all cases linked to 7q (CCM1), but the pathogenesis of CCM is not understood. Krev Interaction Trapped 1 (krit1) was originally identified through its interaction with the Ras-family GTPase krev1/rap1a in a two-hybrid screen, inferring a role in GTPase signaling cascades. We demonstrated additional 5'-coding exons for krit1, extending the N-terminus by 207 amino acids compared to the previously reported protein. Remarkably, by two-hybrid analysis and co-immunoprecipitation, full-length krit1 fails to interact with krev1/rap1a but shows strong interaction with integrin cytoplasmic domain-associated protein-1 (icap1). Icap1 binds to a NPXY motif in the cytoplasmic domain of beta1 integrin and participates in beta1-mediated cell adhesion and migration. The novel N-terminus of krit1 contains a NPXY motif that it is required for icap1 interaction. Like beta1 integrin, krit1 interacts with the 200 amino acid isoform of icap1 (icap1alpha), but not a 150 amino acid form that results from alternative splicing (icap1beta). In a competition assay, induced expression of krit1 diminishes the interaction between icap1alpha and beta1 integrin. Taken together, these data suggest that beta1 integrin and krit1 compete for the same site on icap1alpha, perhaps constituting a regulatory mechanism. Loss-of-function KRIT1 mutations, as observed in CCM1, would shift the balance with predicted consequences for endothelial cell performance during integrin beta1-dependent angiogenesis.

Ventriculopleural shunt obstruction and positive-pressure ventilation. Case report.

The authors report an unusual case of a patient with low-pressure hydrocephalus and a ventriculopleural shunt, in whom routine respiratory management performed using positive-pressure ventilation caused shunt obstruction and coma. While the patient received positive-pressure ventilation with external cerebrospinal fluid (CSF) drainage at subatmospheric pressure, the ventricles returned to normal size and the coma rapidly reversed. After the authors' recognition of the effect of positive-pressure ventilation on intrapleural pressure and ventriculopleural shunt function, and the subsequent removal of positive-pressure ventilation, CSF flow through the shunt resumed and the patient's coma resolved.

ST14A cells have properties of a medium-size spiny neuron.

The ST14A cell line was previously derived from embryonic day 14 rat striatal primordia by retroviral transduction of the temperature-sensitive SV40 large T antigen. We showed that cell division and expression of nestin persists at 33 degrees C, the permissive temperature, whereas cell division ceases, nestin expression decreases, and MAP2 expression increases at the nonpermissive temperature of 39 degrees C. In this study, we further characterized the cells and found that they express other general and subtype-specific neuronal characteristics. ST14A cells express enolase and beta III-tubulin. Furthermore, they express the striatal marker DARPP-32, which is up-regulated upon differentiation of the cells by growth in serum-free medium. Stimulation with dopamine, the D2-dopamine receptor agonist quinpirole, or the D1-dopamine receptor agonist SKF82958 results in phosphorylation of CREB. Treatment of the cells with a mixture of reagents which stimulate the MAPK and adenylyl cyclase pathways radically changes the morphology of the ST14A cells. The cells develop numerous neurite-like appearing processes which stain with beta III-tubulin. Moreover, under these conditions, intracellular injection of rectangular depolarizing current stimuli elicits overshooting action potentials with a relatively fast depolarization rate when starting from a strongly hyperpolarized membrane potential. Taken together, these data imply that the ST14A cell line displays some of the characteristics of a medium-size spiny neuron subtype and provides a new tool to elucidate the pathways and molecules involved in medium-size spiny neuron differentiation and disease.

Hemangioblastomas of the central nervous system in von Hippel-Lindau syndrome and sporadic disease.

OBJECTIVE: The presentation, screening, management, and clinical outcomes of patients who presented to our institution from 1973 to 1999 with central nervous system (CNS) hemangioblastomas in von Hippel-Lindau (VHL) syndrome and sporadic disease were analyzed. METHODS: The surgical pathology database of our institution was searched to identify all patients with histologically verified CNS hemangioblastomas occurring from 1973 to 1999. The medical, radiological, surgical, pathological, and autopsy records from these patients were reviewed retrospectively and statistically analyzed. RESULTS: Forty patients (21 males and 19 females) presented with CNS hemangioblastomas. Twenty-five patients (62%) harbored sporadic hemangioblastomas. Fifteen patients (38%) had VHL syndrome. These 40 patients presented with 61 hemangioblastomas (8 patients had multiple lesions). Ten patients (25%) harbored spinal cord hemangioblastomas (5 patients had multiple lesions). Patients with VHL disease tended to present with neurological symptoms and signs at a younger age than patients with sporadic disease (P = 0.09), to present with multiple lesions (53%), and to develop new lesions (rate, 1 lesion/2.1 yr). Hemangioblastomas of the spinal cord were more prevalent in patients with VHL syndrome (P = 0.024). Neuroradiological screening of patients with VHL syndrome allowed identification of more than 75% of new lesions before they became symptomatic. Sixty-six surgical procedures were performed (12 patients required multiple operations). Six patients with VHL syndrome required surgery for new lesions. Surgical complications occurred in six patients (15%). Symptom resolution or arrest of progression at 1 year was documented in 88% of patients. Recurrence of symptoms from partially resected lesions occurred in eight patients (20%). No deaths associated with surgery occurred. One patient with sporadic disease and one patient with VHL syndrome (5%) died as a result of late medical complications from CNS hemangioblastomas. CONCLUSION: Surgical outcomes for patients with CNS hemangioblastomas are favorable. However, management of hemangioblastomas is a more difficult and prolonged endeavor for patients with VHL syndrome. In patients with VHL syndrome, neuroradiological screening allows identification of lesions before they become symptomatic. Because patients with VHL syndrome are at risk for development of new lesions, they require lifelong follow-up.

The juxtaposition of a capillary telangiectasia, cavernous malformation, and developmental venous anomaly in the brainstem of a single patient: case report.

OBJECTIVE AND IMPORTANCE: Capillary telangiectasias, cavernous malformations, and developmental venous anomalies are all vascular malformations that occur on the capillary-venous side of the cerebral circulation. The associations of capillary telangiectasias with venous malformations, cavernous malformations with venous malformations, and capillary telangiectasias with cavernous malformations have all been described; however, the association of all three lesions in a single patient is extremely rare. CLINICAL PRESENTATION: A 52 year-old Caucasian woman presented to our clinic with an extended history of confusion, distorted visual perceptions, photophobia, neck pain, swallowing problems, and poor balance. The patient's examination was remarkable for difficulty concentrating, mild rotatory nystagmus, subtle decreased sensation over the left side of the face and body, and brisk reflexes. Review of the patient's magnetic resonance imaging examination demonstrated a cavernous malformation, a capillary telangiectasia, and a developmental venous anomaly located adjacent to one another in the brainstem. INTERVENTION: Given the patient's complex constellation of symptoms and relatively mild neurological findings, it was difficult to ascribe any one of them to a specific vascular malformation. Conservative management of this patient's vascular malformations was decided upon. CONCLUSION: Juxtaposition of these three different vascular lesions in the brainstem of an otherwise normal individual suggests a relationship among them. Although there are several theories that link similar associations through physiological mechanisms such as venous hypertension, we propose that a developmental event disrupting local capillary-venous pattern formation is a plausible alternative.

Dynamic nature of cavernous malformations: a prospective magnetic resonance imaging study with volumetric analysis.

OBJECT: Although cavernous malformations (CMs) are not detected in angiographic studies, they have a characteristic appearance on magnetic resonance (MR) images. A number of reports published in the last decade have focused on the behavior of these lesions within the clinical environment. However, little has been published about the evolution of CMs over time, as observed in imaging studies. To understand imaging-documented changes in CMs over time, we analyzed MR images of 114 cavernous malformations in 68 patients who were followed prospectively. METHODS: For each CM the location, volume, and MR imaging signal characteristics were recorded. Volume data were available for 107 lesions from initial images. The mean volume of these 107 CMs was 2779 mm3. The lesions ranged in size from 0.5 to 46,533 mm3 (46.5 cm3). Volume data from a second set of images were available for 76 CMs (mean interval from first imaging session 26 months), and from a third set of images for 24 lesions (mean interval from second imaging session 18 months). Over the first follow-up interval, the mean volume change was -991 mm3 (a decrease of approximately 1 cm3) and over the second interval the mean volume change was -642 mm3. Although these mean volume changes appear modest, volume changes in single lesions during follow-up intervals were more dramatic, with decreases as large as 45,629 mm3 (45.6 cm3) and increases as large as 6,074 mm3 (6 cm3). Serial examinations of the MR imaging signal characteristics of these CMs demonstrate a trend for maturation of blood products from a subacute, to a mixed, and finally to a chronic appearance. Three lesions appeared de novo during the follow-up period. CONCLUSIONS: On the basis of their analysis, the authors conclude that CMs exhibit a range of dynamic behaviors including enlargement, regression, and de novo formation, as well as progression through a series of characteristic MR imaging appearances.

Dominant phenotypes produced by the HD mutation in STHdh(Q111) striatal cells.

Lengthening a glutamine tract in huntingtin confers a dominant attribute that initiates degeneration of striatal neurons in Huntington's disease (HD). To identify pathways that are candidates for the mutant protein's abnormal function, we compared striatal cell lines established from wild-type and Hdh(Q111) knock-in embryos. Alternate versions of full-length huntingtin, distinguished by epitope accessibility, were localized to different sets of nuclear and perinuclear organelles involved in RNA biogenesis and membrane trafficking. However, mutant STHdh(Q111) cells also exhibited additional forms of the full-length mutant protein and displayed dominant phenotypes that did not mirror phenotypes caused by either huntingtin deficiency or excess. These phenotypes indicate a disruption of striatal cell homeostasis by the mutant protein, via a mechanism that is separate from its normal activity. They also support specific stress pathways, including elevated p53, endoplasmic reticulum stress response and hypoxia, as potential players in HD.

Cognitive impairments after surgical repair of ruptured and unruptured aneurysms.

OBJECTIVES: To determine the frequency and severity of neuropsychological impairments associated with aneurysmal subarachnoid haemorrhage, and associated with repair of intracerebral aneurysms. METHODS: Two groups of patients who underwent repair of intracerebral aneurysms were studied: patients with unruptured aneurysms (n=20) and patients with ruptured aneurysms (n=27). All patients were administered a battery of standardised neuropsychological tests about 3 months after surgery. A subset of 12 patients with unruptured aneurysms were administered the battery both before and after elective repair of the aneurysm(s). A subset of six patients with ruptured aneurysms were given the test at both 3 months and 1 year after surgery. RESULTS: As previously reported for patients with ruptured aneurysms, patients with both ruptured and unruptured aneurysms performed, as a group, significantly below published norms on many of the neuropsychological tests after surgery. However, there were significant differences between preoperative and postoperative performance in the unruptured aneurysm group only on a few tests: measures of word fluency, verbal recall, and frontal lobe function. Performance of patients with ruptured aneurysms was significantly below that of patients with unruptured aneurysms only on a few tests of verbal and visual memory. In addition, group differences compared with published norms reflected severely impaired performance by a minority of patients, rather than moderately impaired performance in a majority of patients. CONCLUSIONS: Although patients who undergo repair of ruptured aneurysms perform, as a group, below published norms on many neuropsychological tests, significant impairments are seen in a minority of patients. Some of the impairments are associated with subarachnoid haemorrhage, whereas others (found in patients who underwent repair of unruptured aneurysms) are due to general effects of neurosurgery and perioperative management. Finally, some of the postoperative deficits are merely a reflection of premorbid weaknesses.

Surgical resection of a cerebral arteriovenous malformation for treatment of superficial siderosis: case report.

BACKGROUND: To our knowledge, there are only two reported cases of cerebral arteriovenous malformation associated with superficial siderosis. In both cases, the patients were asymptomatic and were discovered on retrospective review of magnetic resonance imaging. CASE DESCRIPTION: We describe a case of superficial siderosis in a 47-year-old male with a remote history of closed head injury that presented with progressive hearing loss, cerebellar ataxia, and urinary incontinence. Lumbar puncture was indicative of active subarachnoid bleeding. Cerebral angiography revealed a small vascular malformation that was resected. RESULTS: Pathological examination confirmed the diagnosis of the arteriovenous malformation. Six months after surgery the patient is neurologically stable with no further progression of clinical signs or symptoms. CONCLUSIONS: We report the first case of surgical resection of an intracranial arteriovenous malformation for the treatment of superficial siderosis. We emphasize the necessity of a detailed evaluation when superficial siderosis is suspected to localize and resect potential bleeding sources, because the disease is progressive and often irreversible.

Perioperative intracranial hemorrhage in achondroplasia: a case report.

We report a case of a 35-year-old man with achondroplasia who previously had thoracolumbar decompressive laminectomies, who developed recurrence of spinal stenosis at the thoracolumbar junction. The patient underwent standard repeat thoracolumbar decompression, removal of a disc, and spinal fusion with instrumentation in the prone position. Postoperatively the patient was confused. Computed tomography (CT) revealed hemorrhages in both cerebellar hemispheres with surrounding edema and mild mass effect. These were interpreted as venous hemorrhages. Conservative therapy was successful. This is the first case report of perioperative venous intracranial hemorrhage in the context of spinal surgery for achondroplasia. Distinctive anatomic characteristics of achondroplasia, combined with several potentially modifiable aspects of his management, may have predisposed the patient to this complication.

Mutations in KRIT1 in familial cerebral cavernous malformations.

OBJECTIVES: The recognition of six unrelated Hispanic-American families in which cerebral cavernous malformations (CCM) segregated as an autosomal dominant trait established a genetic basis for this disease. Linkage analysis subsequently identified locus heterogeneity with disease genes for CCM at chromosomal regions 7q, 7p, and 3q. Recently, mutations in KRIT1, a gene on 7q at the CCM1 locus, were identified in French and Hispanic-American families with CCM. This study confirms the identity the KRIT1 founder mutation in Hispanic-Americans and reports a novel KRIT1 mutation in a Caucasian family. METHODS: Oligonucleotide primers were designed to allow amplification of genomic DNA sequences from four Hispanic-American families and five non-Hispanic families for all 12 exons of the KRIT1 gene using the polymerase chain reaction (PCR). The amplified DNA was then screened using single strand conformation polymorphism analysis (SSCP) and sequencing. The expression pattern of KRIT1 was analyzed by Northern blotting. RESULTS: Analysis of the KRIT1 gene revealed a point mutation in exon 6 that predicts the substitution of a premature termination codon for glutamine at codon 248 in all four Hispanic-American families, confirming previous findings. SSCP analysis and sequencing revealed an 11 base pair duplication in exon 7 leading to a premature termination codon in one Caucasian family. Northern analysis demonstrated widespread expression of this gene, however, the highest level of expression was in the brain. CONCLUSION: The common KRIT1 mutation causing the majority of CCM in Hispanic-Americans has been identified and independently confirmed, allowing efficient presymptomatic molecular diagnosis. In keeping with prior results, both newly identified mutations create a premature termination codon and are predicted to initiate degradation of the mutant mRNA through the nonsense-mediated mRNA decay pathway. These data strongly suggest loss of function as the relevant patho-genetic mechanism.

Wild-type huntingtin protects from apoptosis upstream of caspase-3.

Expansion of a polyglutamine sequence in the N terminus of huntingtin is the gain-of-function event that causes Huntington's disease. This mutation affects primarily the medium-size spiny neurons of the striatum. Huntingtin is expressed in many neuronal and non-neuronal cell types, implying a more general function for the wild-type protein. Here we report that wild-type huntingtin acts by protecting CNS cells from a variety of apoptotic stimuli, including serum withdrawal, death receptors, and pro-apoptotic Bcl-2 homologs. This protection may take place at the level of caspase-9 activation. The full-length protein also modulates the toxicity of the poly-Q expansion. Cells expressing full-length mutant protein are susceptible to fewer death stimuli than cells expressing truncated mutant huntingtin.

Reoperation for spinal restenosis in achondroplasia.

The characteristics of spinal restenosis in achondroplasia and its treatment are evaluated in this study. Radiologic and surgical findings were correlated to establish the causes of achondroplastic spinal restenosis and the benefits of its therapy. Eight patients (five men, three women) with spinal restenotic complications of achondroplasia were studied. The most common neurological sign of recurrent stenosis was impaired motor function. The mean interval between the most recent surgeries was 8.2 years (9.5 years for surgeries at the same levels). The most common causes of recurrent stenosis were facet hypertrophy and disk disease. The complications were a dural tear and cerebellar hemorrhage in one patient and transient neurological deterioration in another. One patient died after operation. Restenosis can occur many years after original decompression in the achondroplastic spine, and repeated operation can successfully lessen pain and neurological symptoms in most patients.