[Intraoperative Monitoring During Microvascular Decompression].

During microvascular decompression(MVD)for hemifacial spasm(HFS), trigeminal neuralgia(TN), and glossopharyngeal neuralgia(GPN), brainstem auditory-evoked potential monitoring is widely used to preserve hearing function. In MVD for HFS, abnormal muscle response monitoring is useful for identifying the offending vessels compressing the facial nerve and confirming the completion of decompression intraoperatively. The amplitude of facial motor-evoked potential by transcranial electrical stimulation in the orbicularis oculi muscle is reported to decrease after completing MVD. The Z-L response(ZLR)probably confirms the true offending vessels by stimulating the culprit vessels; then, the ZLR could disappear after decompressing the offending vessels away from the compression sites. Spontaneous electromyographic activities obtained from the mentalis muscles by injection of saline into the facial nerve reportedly decreased after MVD compared with those before MVD. In MVD for the GPN, glossopharyngeal motor-evoked potential by transcranial electrical stimulation is used to preserve swallowing function and not to assess the completion of MVD. Because MVD for both the TN and GPN can result in normalization of the hyperactivity of the sensory nerve, it may be difficult to develop any monitoring to confirm the completion of MVD during surgery.

JNK1-Dependent Phosphorylation of GAP-43 Serine 142 is a Novel Molecular Marker for Axonal Growth.

Mammalian axon growth has mechanistic similarities with axon regeneration. The growth cone is an important structure that is involved in both processes, and GAP-43 (growth associated protein-43 kDa) is believed to be the classical molecular marker. Previously, we used growth cone phosphoproteomics to demonstrate that S96 and T172 of GAP-43 in rodents are highly phosphorylated sites that are phosphorylated by c-jun N-terminal protein kinase (JNK). We also revealed that phosphorylated (p)S96 and pT172 antibodies recognize growing axons in the developing brain and regenerating axons in adult peripheral nerves. In rodents, S142 is another putative JNK-dependent phosphorylation site that is modified at a lower frequency than S96 and T172. Here, we characterized this site using a pS142-specific antibody. We confirmed that pS142 was detected by co-expressing mouse GAP-43 and JNK1. pS142 antibody labeled growth cones and growing axons in developing mouse neurons. pS142 was sustained until at least nine weeks after birth in mouse brains. The pS142 antibody could detect regenerating axons following sciatic nerve injury in adult mice. Comparison of amino acid sequences indicated that rodent S142 corresponds to human S151, which is predicted to be a substrate of the MAPK family, which includes JNK. Thus, we confirmed that the pS142 antibody recognized human phospho-GAP-43 using activated JNK1, and also that its immunostaining pattern in neurons differentiated from human induced pluripotent cells was similar to those observed in mice. These results indicate that the S142 residue is phosphorylated by JNK1 and that the pS142 antibody is a new candidate molecular marker for axonal growth in both rodents and human.

The Real-World status and risk factors for a poor prognosis in elderly patients with primary central nervous system malignant lymphomas: a multicenter, retrospective cohort study of the Tohoku Brain Tumor Study Group.

BACKGROUND: Elderly patients with primary central nervous system malignant lymphoma (EL-PCNSL) may not be given sufficient treatment due to their poor pre-treatment Karnofsky Performance Status (KPS) and comorbidities. Therefore, a retrospective, cohort study was performed to evaluate risk factors associated with a poor prognosis of EL-PCNSL in the Tohoku Brain Tumor Study Group. METHODS: Patients aged ≥ 71 years with PCNSL were enrolled from eight centers. Univariate analysis was performed with the log-rank test. A Cox proportional hazards model was used for multivariate analysis. RESULTS: Three of the total 142 cases received best supportive care (BSC). Treatment was given to 30 cases without a pathological diagnosis, 3 cases with cerebrospinal fluid (CSF) cytology, and 100 cases with a pathological diagnosis. After confirmation of no differences in progression-free survival (PFS) and overall survival (OS) between the group treated without pathology and the groups diagnosed by pathology or CSF cytology and between median age ≥ 76 years and < 76 years, a total of 133 patients were studied. The median pre-treatment KPS was 50%. Median PFS and median OS were 16 and 24 months, respectively. Risk factors associated with poor prognosis on Cox proportional hazards model analysis were pre-treatment cardiovascular disease and central nervous system disease comorbidities, post-treatment pneumonia and other infections, and the absence of radiotherapy or chemotherapy. CONCLUSIONS: Pre-treatment comorbidities and post-treatment complications would affect the prognosis. Radiation and chemotherapy were found to be effective, but no conclusions could be drawn regarding the appropriate content of chemotherapy and whether additional radiotherapy should be used.

Elucidating the multiple genetic alterations involved in the malignant transformation of a KRAS mutant neurenteric cyst. A case report.

Neurenteric cyst (NC) shows benign histopathology and rarely demonstrate malignant transformation. We herein describe a case of NC that exhibited malignant transformation. A 65-year-old female presented with gait disturbance due to compression by a cystic mass on the dorsal surface of the medulla oblongata. Partial resection was performed twice, leading to improvement of her symptoms. Two years after the second surgery, gadolinium-perfused T1-weighted magnetic resonance imaging revealed an invasive lesion with contrast enhancement at the trigone of the left lateral ventricle for which partial resection followed by radiotherapy was performed. However, mass regrowth was observed, with the patient eventually succumbing to her disease 11 months after her third surgery. Histopathological analyses of the first and second surgical specimens identified pseudostratified cuboidal epithelial cells, with no nuclear or cellular atypia resembling gastrointestinal mucosa, lining the inner surface of the cystic wall. Based on these findings the lesion was diagnosed as NC. The third surgical specimen exhibited apparent malignant features of the epithelial cells with elongated and hyperchromatic nuclei, several mitotic figures, small necrotic foci, and a patternless or sheet-like arrangement. Based on these findings, the lesion was diagnosed as NC with malignant transformation. Next-generation sequencing revealed KRAS p.G12D mutation in all specimens. Additionally, the third surgical specimen harbored the following 12 de novo gene alterations: ARID1A loss, BAP1 p.F170L, CDKN1B loss, CDKN2A loss, CDKN2B loss, FLCN loss, PTCH1 loss, PTEN loss, PTPRD loss, SUFU loss, TP53 loss, and TSC1 loss. The aforementioned results suggest that KRAS mutation is associated with the development of the NC, and that the additional gene alterations contribute to malignant transformation of the NC.

Endovascular treatment of an infectious aneurysm using the selective provocative test and transcranial motor evoked potential monitoring under general anesthesia: a case report.

The selective provocative test (SPT) under local anesthesia aids in protecting against ischemic complications during endovascular treatment. However, the use of this test under general anesthesia is not well described. Herein, we present a case of a 51-year-old man with a ruptured fusiform aneurysm in the middle cerebral artery M4 segment, which was thought to possibly supply the motor cortex. Internal trapping of the affected vessel and aneurysm by endovascular intervention was successfully performed after SPT using transcranial motor evoked potential (MEP) monitoring under general anesthesia. Transcranial MEP is suitable for neurological assessment during SPT under general anesthesia.

[Intraoperative Neuromonitoring for Skull Base Surgery].

Intraoperative neuromonitoring techniques can be used to evaluate neural functions during surgical procedures. For removal of tumors in the skull base region, we perform them for both structural mapping of the compressed cranial nerves and continuous monitoring of their preservation. The goal is to eliminate the critical irreversible damage to the neurological structures and prevent postoperative neurologic deficits. Recording techniques have been developed and neuromonitoring equipment used in the operation room with the intravenous anesthesia technique. For skull base surgery, in particular, the neuromonitoring contains motor evoked potential(MEP), brainstem auditory evoked potential(BAEP), visual evoked potential(VEP), and others. We believe that the appropriate recording and interpretation of these data can greatly improve the surgical outcomes of tumor removal and prevent postoperative neurologic deficits.

Unilateral oculomotor nerve palsy caused by arterial compression accompanying subarachnoid hemorrhage: a case report.

Unilateral oculomotor nerve palsy, often caused by aneurysmal compression, is one of the decisive findings for confirming the site of a ruptured aneurysm. However, arterial compression can also cause unilateral oculomotor nerve palsy. Here, we present the case of a 59-year-old woman with a ruptured right internal carotid-posterior communicating artery aneurysm accompanied by contralateral oculomotor nerve palsy. The nerve was found to be compressed by the posterior cerebral artery and was isolated from the ruptured aneurysm. When confirming a ruptured aneurysm based on the evidence of unilateral oculomotor palsy, the arteries surrounding the nerve must be thoroughly assessed.

[Multinodular and Vacuolating Neuronal Tumor of the Cerebrum(MVNT)].

Multinodular and vacuolating neuronal tumors of the cerebrum(MVNTs)are rare brain tumors that were described first in 2013. MVNTs have been added to the World Health Organization Classification of Tumors of the Central Nervous System in 2016(2016WHO), although an MVNT is a clinical-pathological lesion with uncertain class assignment. It remains unclear whether MVNTs should be considered a true neoplasm or malformative lesion. Their prevalence and pathophysiology are unknown. MVNTs typically occur in adults, predominantly in the cerebral subcortical region, and are most frequently associated with seizures or seizure equivalents. MVMTs can also present incidentally without seizures. MVNTs have been reported to show highly suggestive imaging features, especially on MRI scans. MVNTs consist of small T2 and T2-FLAIR hyperintense nodules in subcortical and juxtacortical areas with rare or no post-contrast enhancement. Most MVNTs reported in the literature involve the supratentorial part of the brain. Recently, lesions exhibiting a remarkably similar pattern of imaging findings were described in the posterior fossa, which are referred to as multinodular and vacuolating posterior fossa of unknown significance(MV-PLUS). Both MVNT and MV-PLUS are considered "leave-me-alone" lesions because of the absence of malignancy criteria and the lack of evolutivity on follow-up MRI scans.

[Melanocytic Tumors].

Primary melanocytic neoplasms of the central nervous system(CNS)presumably arise from leptomeningeal melanocytes that are derived from the neural crest. Melanocytic neoplasms associated with neurocutaneous melanosis likely derive from melanocyte precursor cells that reach the CNS after somatic mutations, mostly, of the NRAS. They should be distinguished from other melanotic tumors involving the CNS, including metastatic melanoma and other primary tumors that undergo melanization, such as melanocytic schwannomas, medulloblastomas, paragangliomas, and various gliomas, because these lesions require different patient workups and therapy. Primary melanocytic neoplasms of the CNS that are diffuse and do not form macroscopic masses are called melanocytoses, whereas malignant diffuse or multifocal lesions are collectively called melanomatoses. Benign and intermediate-grade tumoral lesions are called melanocytomas. Discrete malignant tumors are called melanomas. CT and MRI of melanocytosis and melanomatosis show diffuse thickening and enhancement of the leptomeninges, often with focal or multifocal nodularity. Depending on the melanin content, diffuse and circumscribed melanocytic tumors of the CNS may show some characteristics on CT and MRI: iso- to hyperattenuation on CT and paramagnetic properties of melanin on MRI resulting in an isointense signal on T1WIs and iso- to hypointensity on T2WIs.

[Dysplastic Cerebellar Gangliocytoma(Lhermitte-Duclos Disease)].

Dysplastic cerebellar gangliocytoma or Lhermitte-Duclos disease(LDD)is a rare benign cerebellar lesion composed of dysplastic ganglion cells that conform to the existing cortical architecture. In this disease, the enlarged ganglion cells are predominantly located within the internal granular layer, and they thicken the cerebellar folia. The architecture of the affected cerebellar hemisphere with the enlarged cerebellar folia and the cystic changes, in some cases, present as "tiger-striped striations," a characteristic imaging finding that is not specific to LDD. This imaging feature may be observed in medulloblastoma and isolated cerebellar Rosai-Dorfman disease. This cerebellar lesion is a major central nervous system manifestation of Cowden syndrome, an autosomal dominant condition that causes various hamartomas and neoplasms. A molecular-based study estimated the prevalence of Cowden syndrome to be 1 case per 200,000. In a study involving 211 patients with Cowden syndrome, 32% developed LDD. LDD can be diagnosed in young children and older adults within the eighth decades of life. PTEN mutations have been identified in virtually all adult-onset LDDs, but not in childhood-onset cases.

[Proton magnetic resonance spectroscopy (1H-MRS)].

Proton magnetic resonance spectroscopy(1H-MRS)is a non-invasive method for evaluating brain function and metabolism. 1H-MRS can quantify low-molecular-weight metabolites in a living brain; it shows their spectra without tracer administration. In this paper, we introduce 1H-MRS and MRS for imaging the distribution of metabolites. The applications of 1H-MRS imaging for several neurological disorders will be outlined.

[The Present and Future of Less-invasive Liquid Biopsy for the Diagnosis of Gliomas and Brain Tumors].

There is growing interest in liquid biopsy, the less-invasive detection of circulating tumor DNA(ctDNA)or circulating tumor cells(CTCs)from cerebrospinal fluid(CSF)and/or serum of patients, for the diagnosis of brain tumors. We share our experience of detecting hot spot point mutations using droplet digital PCR(ddPCR)in ctDNA obtained from the CSF of patients with brain tumors. The detection of mutations such as IDH1 R132H, BRAF V600E, and TERT promoter mutations in gliomas can be diagnostic. For optimal detection of ctDNA, which is only seen at very low concentrations, proper handling and storage of CSF, high-yield extraction of ctDNA, and usage of sensitive PCR methods for detection are imperative. We discuss which mutations can be assessed when diagnosing brain tumors, with a specific focus on gliomas. Finally, we look at what the near future holds for liquid biopsy of brain tumor patients, including next-generation sequencing panel analysis and accurate assessment of fusion genes.

Expression of the ghrelin/growth hormone secretagogue receptor axis and its functional role in promoting tumor growth in primary central nervous system lymphomas.

Ghrelin and its receptor, growth hormone secretagogue receptor (GHS-R), have been found in a variety of malignant tumor tissues, suggesting a biological function of the ghrelin/GHS-R axis in tumor growth and progression. Among central nervous system tumors, primary central nervous system lymphomas (PCNSLs) are relatively rare and characterized by a rapid progression and poor prognosis. In order to clarify ghrelin expression and its functional role in promoting tumor growth and progression in PCNSLs, we undertook an immunohistochemical investigation for ghrelin and GHS-R expression in 43 patients and tested the effect of ghrelin inhibition on lymphoma cells. Furthermore, we investigated the expression of CD105, a marker for tumor angiogenesis, to explore its association with the ghrelin/GHS-R axis. The Kaplan-Meier method and Cox's proportional hazards regression model were used to determine the association of ghrelin/GHS-R expression with overall survival rate. The immunohistochemical study showed moderate/strong immunostaining of cells for ghrelin and GHS-R in 40 patients (93.0%) and 39 patients (90.7%), respectively. A ghrelin inhibitor did not affect tumor cell proliferation in vitro. Expression levels of ghrelin and GHS-R were divided into high and low groups by the rate of moderate-strong staining cells to tumor cells. The survival rate was significantly lower in patients with high GHS-R expression (P = 0.0368 by log-rank test; P = 0.0219 by Wilcoxon test). In addition, multivariate analysis of overall survival using Cox's proportional hazards regression model indicated that GHS-R was a significant independent prognostic factor (P = 0.0426). CD105 expression on tumor vessels was positive in 33 patients (33/37, 89.2%). There was a positive correlation between the moderate-strong staining rate of ghrelin and CD105-positive vessel count. These results indicated that the ghrelin/GHS-R axis plays a potential role in promoting tumor growth and progression through neoangiogenesis, rather than the proliferation of tumor cells.

Vascular Hyperintensity on Fluid-Attenuated Inversion Recovery Indicates the Severity of Hypoperfusion in Acute Stroke.

BACKGROUND AND AIM: Although fluid-attenuated inversion recovery vascular hyperintensities may be frequently seen in acute large-artery ischemic stroke, reports on their prognostic utility had been conflicting due to lack of quantitative evaluation of the perfusion status based on the signal intensity. We hypothesized that greater hyperintensity represents more severe hypoperfusion. METHODS: Overall, 27 patients with acute occlusion of the proximal middle cerebral artery were divided into 2 groups, based on their signal intensity in the insular segment of middle cerebral artery on the affected side, relative to that of the insular cortex: the low signal intensity group (hypo- or isointense signals, n = 12) and the high signal intensity group (hyperintense signals, n = 15). Using dynamic susceptibility contrast magnetic resonance imaging, we assessed the time of the maximum value of the residue function and mean transit time, in the entire middle cerebral artery cortical area and diffusion-weighted imaging-Alberta Stroke Program Early Computed Tomography Score regions, including the corona radiata. RESULTS: The high signal intensity group had significantly longer time of the maximum value of the residue function in all the diffusion-weighted imaging-Alberta Stroke Program Early Computed Tomography Score regions, except the M3 and M6 regions, and significantly longer mean transit time in the M1 and M4 regions. CONCLUSIONS: Quantitative analysis of the perfusion parameters revealed more severely compromised and widely disturbed perfusion status in the high signal intensity group than in the low signal intensity group.

[Endovascular Revascularization for Acute Ischemic Stroke Related to Blunt Carotid Injury:A Case Report].

Although blunt carotid artery injury is known as an important cause of ischemic stroke, the role of the endovascular treatment for acute ischemic stroke related to blunt carotid injuries remains unclear. We report the case of a patient with acute ischemic stroke secondary to blunt carotid artery injury who was treated with endovascular revascularization. A 46-year-old man suffered from sudden left-sided hemiparesis a day after a strike from a Japanese fencing staff on his right neck. 3D-CT angiography revealed tandem internal carotid artery occlusions of the cervical and C1 portions. We performed endovascular revascularization with carotid artery stenting and direct aspiration of the thrombus and achieved complete recanalization. The patient recovered almost completely. We conclude that endovascular revascularization should not be withheld from patients with acute ischemic stroke related to blunt carotid injury.

Noninvasive Vagus Nerve Stimulation Prevents Ruptures and Improves Outcomes in a Model of Intracranial Aneurysm in Mice.

Background and Purpose- Inflammation is a critical determinant of aneurysmal wall destabilization, growth, and rupture risk. Targeting inflammation may suppress aneurysm rupture. Vagus nerve stimulation (VNS) has been shown to suppress inflammation both systemically and in the central nervous system. Therefore, we tested the effect of a novel noninvasive transcutaneous VNS approach on aneurysm rupture and outcome in a mouse model of intracranial aneurysm formation with wall inflammation. Methods- Aneurysms were induced by a single stereotaxic injection of elastase into the cerebrospinal fluid at the skull base, combined with systemic deoxycorticosterone-salt hypertension, without or with high-salt diet, for mild or severe outcomes, respectively. Cervical VNS (two 2-minute stimulations 5 minutes apart) was delivered once a day starting from the day after elastase injection for the duration of follow-up. Transcutaneous stimulation of the femoral nerve (FNS) served as control. Multiple aneurysms developed in the circle of Willis and its major branches, resulting in spontaneous ruptures and subarachnoid hemorrhage, neurological deficits, and mortality. Results- In the milder model, VNS significantly reduced aneurysm rupture rate compared with FNS (29% versus 80%, respectively). Subarachnoid hemorrhage grades were also lower in the VNS group. In the more severe model, both VNS and FNS arms developed very high rupture rates (77% and 85%, respectively). However, VNS significantly improved the survival rate compared with FNS after rupture (median survival 13 versus 6 days, respectively), without diminishing the subarachnoid hemorrhage grades. Chronic daily VNS reduced MMP-9 (matrix metalloproteinase-9) expression compared with FNS, providing a potential mechanism of action. As an important control, chronic daily VNS did not alter systemic arterial blood pressure compared with FNS. Conclusions- VNS can reduce aneurysm rupture rates and improve the outcome from ruptured aneurysms.

Multiplex ligation-dependent probe amplification analysis is useful for detecting a copy number gain of the FGFR1 tyrosine kinase domain in dysembryoplastic neuroepithelial tumors.

PURPOSE: Dysembryoplastic neuroepithelial tumors (DNTs) are slow-growing glioneuronal tumors, and their genetic backgrounds are getting unveiled. Recently, fibroblast growth factor receptor 1 internal tandem duplication (FGFR1-ITD) of the tyrosine kinase domain (TKD) has been demonstrated by whole-genome sequencing. METHODS AND RESULTS: Here, we analyzed 22 DNTs using multiplex ligation-dependent probe amplification (MLPA) with formalin-fixed paraffin-embedded specimens and found a copy number gain in TKD of FGFR1 (13 cases, 59%), which suggested the presence of FGFR1-ITD. Another 5 DNTs harbored FGFR1 hot spot mutations including a double mutant case, and FGFR1 alterations were detected in 18 DNTs (82%). The BRAF V600E mutation, another important mutation in DNTs, was not observed. CONCLUSIONS: With recent findings of less frequent or absent FGFR1-ITD in pilocytic astrocytomas or rosette-forming glioneuronal tumors, the analysis of FGFR1 aberrations, especially FGFR1-ITD, was suggested to be helpful to discriminate DNTs from their histological mimics.

[Posterior Quadrantectomy for Infant with Refractory Epilepsy:A Case Report].

We present the case of an 11-month-old girl with linear nevus sebaceous syndrome who underwent posterior quadrantectomy(PQ)for intractable epilepsy due to cortical dysplasia extending from the temporal, parietal, and occipital lobes in the right hemisphere. Epileptic spasms started at 4 months after birth, and the frequency of her seizures gradually increased to 10 episodes per day. Electroencephalograms in the interictal periods showed hypsarrhythmia. Magnetic resonance imaging(MRI)suggested cortical dysplasia in the right temporal, parietal, and occipital lobes. Ictal single-photon emission computed tomography revealed increased cerebral blood flow in similar areas as the cortical dysplasia suggested on MRI. Several antiepileptic drugs were administered to control the epileptic spasms, without success. In addition, her developmental delay gradually became evident. Because the epileptic foci extended into the posterior region of the right hemisphere, we did not execute a focused resection, but performed a PQ. The epileptic spasms completely disappeared after surgery and her developmental delay gradually improved. Early surgical intervention via PQ is useful in patients with drug-resistant epilepsy in whom the epileptic foci have extended into the temporal, parietal, and occipital lobes. This intervention not only controls intractable seizures but also helps to facilitate normal development.

The perivascular microenvironment in Epstein-Barr virus positive primary central nervous system lymphoma: The role of programmed cell death 1 and programmed cell death ligand 1.

It has been shown that high expression of certain immune checkpoint molecules, including those of the programmed death protein 1/programmed death ligand 1 (PD-1/PD-L1) axis, can be utilized to regulate immunosuppression in the microenvironment of malignant neoplasms. For the purpose of clarifying the immune-escape mechanism of primary central nervous system lymphomas (PCNSLs), particularly in Epstein-Barr virus (EBV)-positive cases, markers for PD-1, PD-L1, tumor-associated macrophages (TAMs), and tumor-infiltrating lymphocytes (TILs) in 39 surgical specimens of PCNSLs (17 EBV-positive, 22 EBV-negative) were investigated by immunohistochemistry. Staining for PD-L1 was scored as follows: (-), no staining; (1+), 0-30% positive cells; (2+), 30-60% positive cells; and (3+), >60% positive cells. In EBV-positive cases, PD-L1 was detected in both lymphoma cells and TAMs in 12/17 cases, and in TAMs only in 4/17 cases. The mean number of PD-1, TIA-1 (a marker for cytotoxic T-cells), and FOXP3 (a marker for regulatory T-cells)-positive TILs in EBV-positive cases was 36.4 ± 45.9, 390 ± 603, and 9.88 ± 15.1, respectively. In EBV-negative cases, PD-L1 was detected in both lymphoma cells and TAMs in 11/22 cases, and in TAMs only in 4/22 cases. The mean of PD-1, TIA-1 and FOXP3-positive lymphocytes in EBV-negative cases was 67.3 ± 82.0, 158 ± 206 and 9.32 ± 17.5, respectively. We found no significant difference in the number of FOXP3-positive, lymphocytes between EBV-positive and negative cases. However, there were significantly higher numbers of PD-1-positive lymphocytes in the former, and significantly higher numbers of TIA-1-positive lymphocytes in the latter (P < 0.05). The combined data indicate that expression of PD-L1 by lymphoma cells and TAMs mediate the trafficking of TILs, which may explain the immune-escape process of PCNSLs. In addition, EBV infection appears to affect the trafficking mechanism of TILs, and may thus play an important role in the microenvironment immunity of these tumors.

Polysomnography as an indicator for cervicomedullary decompression to treat foramen magnum stenosis in achondroplasia.

OBJECTIVE: Management of cervicomedullary compression due to foramen magnum stenosis in achondroplasia remains controversial, especially for patients with no symptoms or mild symptoms. We examined the effectiveness of polysomnography (PSG) as an indicator for cervicomedullary decompression treatment. METHODS: We retrospectively reviewed nine achondroplasia cases (mean age 1 year and 9 months) treated from 2008 to 2015. All patients were examined by PSG, magnetic resonance imaging (MRI), and otolaryngeal fibroscopy. We analyzed demographic data, clinical presentation, degree and type of respiratory impairment, severity of foramen magnum stenosis and concomitant cervicomedullary compression, treatment (conservative or surgical), and clinical outcome. RESULTS: Eight of nine patients presented with no severe symptoms in the daytime. However, MRI revealed four severe, four moderate, and one mild case of cervicomedullary compression, and PSG demonstrated severe sleep apnea in four cases and moderate sleep apnea in five cases. All sleep apnea cases were obstructive or obstructive-dominant. Fibroscopy revealed no upper airway stenosis in six cases and mild stenosis in three cases. Four patients who had severe sleep-related respiratory disturbance on PSG and severe or moderate cervicomedullary compression were treated by cervicomedullary decompression. Three of these patients demonstrated improved sleep respiration soon after surgery, while one required temporary tracheostomy due to bilateral vocal cord paralysis caused by compression during intratracheal intubation. CONCLUSION: Polysomnography can be a useful indicator for cervicomedullary decompression surgery, especially in cases of seemingly asymptomatic achondroplasia with severe foramen magnum stenosis.