Sestd1 Encodes a Developmentally Dynamic Synapse Protein That Complexes With BCR Rac1-GAP to Regulate Forebrain Dendrite, Spine and Synapse Formation

SEC14 and Spectrin domain-1 (Sestd1) is a synapse protein that exhibits a striking shift from the presynaptic to postsynaptic space as neurons mature postnatally in the mouse hippocampus. Hippocampal pyramidal neurons from mice with global genetic deletion of Sestd1 have reduced dendrite arbors, spines, and excitatory synapses. Electrophysiologically this correlates with cell-autonomous reductions in both AMPA- and NMDA-excitatory postsynaptic currents in individual hippocampal neurons from which Sestd1 has been deleted in vivo. These neurodevelopmental and functional deficits are associated with increased activation of the Rho family GTPases Rac1 and RhoA. Co-immunoprecipitation and mass spectrometry reveal that the Breakpoint Cluster Region protein, a Rho GTPase activating protein (GAP), forms complexes with Sestd1 in brain tissue. This complements earlier findings that Sestd1 can also partner with other Rho family GAPs and guanine nucleotide exchange factors. Our findings demonstrate that Sestd1 is a developmentally dynamic synaptic regulator of Rho GTPases that contributes to dendrite and excitatory synapse formation within differentiating pyramidal neurons of the forebrain.

The Planar Cell Polarity Transmembrane Protein Vangl2 Promotes Dendrite, Spine and Glutamatergic Synapse Formation in the Mammalian Forebrain

The transmembrane protein Vangl2, a key regulator of the Wnt/planar cell polarity (PCP) pathway, is involved in dendrite arbor elaboration, dendritic spine formation and glutamatergic synapse formation in mammalian central nervous system neurons. Cultured forebrain neurons from Vangl2 knockout mice have simpler dendrite arbors, fewer total spines, less mature spines and fewer glutamatergic synapse inputs on their dendrites than control neurons. Neurons from mice heterozygous for a semidominant Vangl2 mutation have similar but not identical phenotypes, and these phenotypes are also observed in Golgi-stained brain tissue from adult mutant mice. Given increasing evidence linking psychiatric pathophysiology to these subneuronal sites and structures, our findings underscore the relevance of core PCP proteins including Vangl2 to the underlying biology of major mental illnesses and their treatment.

Endoscopic anatomy of the sphenoid sinus and sella turcica

An endoscopic study of the sphenoid sinus was carried out, on 30 cadavers, to understand the important anatomical relationships of the sphenoid sinus, and the sella turcica. The aim was to study the endoscopic anatomy and the variants, and to determine if endoscopic instrumentation and techniques, could play a beneficial role in endoscopic management of sellar lesions. The results of this study are discussed, with particular reference to the important surgical anatomical features of the sphenoid sinus. A surgical technique for the endoscopic transsphenoid approach to the sella turcica was developed. Anatomical variants can be identified endoscopically, and endoscopic techniques have the advantages of improved visualization, magnification, angled vision, and a panoramic perspective of the intrasphenoid anatomy, compared to currently employed methods of pituitary/sellar surgery, using the operating microscope.

Stapedectomy at the Singapore General Hospital--use of functional hearing analysis

The results of stapedectomy surgery performed in Singapore General Hospital covering a period of over two years are reviewed. The diagnostic importance of selected clinical features and investigative procedures in otosclerosis is studied. The post-operative hearing status of twenty-six cases of primary stapedectomy is analysed using traditional audiometric and modern functional methods. Seventeen patients (65.4%) achieved closure of air-bone gap to less than 10 dB while the overall mean hearing gain was 28.6 dB. Using the Glasgow Plot parameter, 73.1% showed significant benefit from surgery, whilst the corresponding figure using the Belfast Rule of Thumb assessment technique was 57.7%. The validity of the foregoing evaluation techniques is compared. Different operative techniques, including variations in fenestra size and method of oval window seal showed statistically similar results. The scarcity of stapedectomy cases poses problems in the training of future specialists.

Deep neck abscesses--changing trends

A retrospective review was conducted of 64 patients with deep neck abscesses. Based on clinical and operative findings, these abscesses were categorized as retropharyngeal abscess (29 patients), parapharyngeal abscess (10 patients), Ludwig's angina (19 patients), or necrotizing cervical fasciitis (six patients). Regional trauma from an ingested foreign body was the cause for 59 per cent of the patients with a retropharyngeal abscess. In 90 per cent of subjects with Ludwig's angina, an odontogenic cause was established; however, in the majority of cases of parapharyngeal abscess (80 per cent) and necrotizing fasciitis of the neck (85 per cent), aetiology was unknown. Fifty-five patients (86 per cent) required open neck drainage. In the remaining nine (14 per cent) endoscopic drainage of the abscess was possible. Eight patients (12 per cent) needed a tracheotomy for airway control. The overall mortality was eight per cent despite aggressive anti-microbial therapy and early surgical intervention. Thirty-four cultures grew aerobic organisms. Seventy-six per cent of these were gram-negative microorganisms. The bacteriological pattern of deep neck abscesses is changing and may be responsible for the considerable mortality rate with which the abscesses are still associated despite anti-microbial therapy.

Malignant mesenchymoma of the retropharyngeal space

Malignant mesenchymoma is a very rare head and neck tumour. To date only 15 cases have been reported in world literature and all in children under 16 years of age. We present here a case of a 40-year-old man with malignant mesenchymoma of the retropharyngeal space. The clinical picture is that of progressive dysphagia, voice change, snoring and dyspnoea. CT scan showed a soft tissue space-occupying lesion of the retropharyngeal space which enhanced very well with intravenous contrast. The tumour was excised in toto and the patient given post-operative radiotherapy. Histopathology showed two unrelated differentiated tissue types (bone and fat) in addition to the fibrosarcomatous element thus satisfying Stout's criteria (Stout, 1948) for a diagnosis of malignant mesenchymoma.

Migrating foreign bodies in the upper digestive tract

Migrating foreign bodies in the aerodigestive tract are not so uncommon. Two cases of penetrating and migrating extraluminal foreign bodies in the upper aerodigestive tract are presented. Both patients had ingested fish bones. Fish bones are the commonest of bones to be ingested. Sharp and pointed fish bones are more likely to penetrate extraluminally. A high index of suspicion is necessary to institute early treatment. A CAT scan is invaluable in locating the foreign body especially with regards to surgical landmarks at exploration. Early surgical intervention avoids life-threatening complications.

View from beneath: pathology in focus. Synovial sarcoma of hypopharynx

Synovial sarcoma of the hypopharynx is a rare neoplasm. To date only 23 cases of synovial sarcoma of the hypopharynx have been reported in the literature. An additional case in an 18-year-old male is presented. This is the first case of synovial sarcoma in the hypopharynx to be reported in Singapore. The presentation was that of a mass in the hypopharynx; progressive dysphagia, intermittent hoarseness and gradual airway compromise. A CT scan was valuable in determining the site of origin and extent of the lesion. Histopathology was diagnostic. Treatment comprised of wide surgical excision of the tumour and post-operative radiotherapy.

Parapharyngeal abscesses

Fifty-five patients with deep neck infections treated consecutively over a period of six and a half years between January 1983 and July 1989 were reviewed. Nine of these patients had abscesses localized to the pharapharyngeal space and form the basis of this study. The aetiology of the parapharyngeal abscess was odontogenic in two patients and remained unknown in the other seven. Five patients had associated systemic disease; four were diabetics and one patient had non-Hodgkin's Lymphoma. High dosage intravenous antibiotics directed towards the causative micro-organisms, airway control and early surgical intervention was the mainstay of treatment. All patients underwent open surgical drainage of the parapharyngeal abscess within 24 h of admission. Bacteriology results showed Klebsiella sp. to be the dominant micro-organism cultured in four patients. Morbidity was low; seven patients had no post-operative complications and were discharged from the hospital between 7-24 d (mean 12.9 d). There were two deaths. Early open surgical drainage remains the most appropriate method of treating parapharyngeal space infections; it avoids life threatening complications with rapid recovery.

Parapharyngeal space tumours

Parapharyngeal space tumours are rare, forming 0.5% of all head and neck tumours. They are of interest because of the varied histological types, diagnostic puzzle and challenge at surgical excision. Thirteen patients, seen over an eight year period (from 1981 to 1988) in the Department of Otolaryngology, Singapore General Hospital, are presented. Clinically most patients presented with a painless upper neck lump and on examination, a lateral pharyngeal wall bulge was noted. The main investigation after ruling out a nasopharyngeal primary tumour is a high resolution Computer Tomographic (CT) scan with intravenous contrast. Only if a vascular tumour is suspected on CT scanning, should angiography be performed. Pathologically, the commonest tumours are salivary gland tumours, neurolemmomas and paragangliomas. The surgical approaches at removing these tumours are discussed, emphasising maximal exposure and control of the vascular structures in the head and neck. Recognising these tumours enable the correct sequence of investigations to be performed rather than a 'lymph node' biopsy or 'tonsillectomy' which may be done resulting in an increased morbidity for the patient and an embarrassment for the attending physician.

Acute epiglottitis in adults (the Singapore experience)

Acute epiglottitis in adults is a potentially fatal but self-limiting disease of increasing incidence world-wide. Forty-two patients, seen consecutively over a four year period at the ENT Department, Singapore General Hospital were reviewed retrospectively. A strong male predominance with a peak age incidence in the sixth decade was noted. A severe sore throat and dysphagia with disproportionate signs of oropharyngeal inflammation was the main presenting picture. Only three patients had stridor on presentation. Vigilant monitoring of the airway with empirical high-dose intravenous ampicillin, cloxacillin and steroids resulted in a dramatic clinical improvement in most patients and none developed stridor after admission. The yield from throat swabs and blood cultures were low. Two patients developed complications, a Ludwigs angina and an epiglottic abscess. Recurrent epiglottitis was a problem in one patient. There was low morbidity and no mortality on the management regime outlined.

Radiotherapy of early glottic cancer Singapore, 1978-1981

This study analyses the results of primary radiotherapy for 44 patients with early glottic cancer (Tis, T1 stage) given at the Therapeutic Radiology Department, Singapore General Hospital during the 4-year period from 1978 to 1981. Irradiation was delivered using cobalt teletherapy with free set-ups, and without "air-gap" compensation. Total doses of 55Gy to 64Gy were given in daily fractions of 1.8Gy, treating five times a week. The crude 5-year survival rate for Tis/T1a tumours was 88.9% and for T1b lesions, 81%. On correcting for deaths from intercurrent disease, the survival rates improved to 95.5% and 92.6% respectively. In 33 cases where the quality of voice after radiation was assessed, 15 patients (45.4%) retained good voice quality with an additional 11 patients (33.3%) having acceptable voice quality. In seven cases the voice after radiation was rated as poor. Nine patients had local recurrence, giving a rate of 20.4%. One other patient had cervical node metastasis and subsequently developed lung secondaries. Surgery, solely or with re-irradiation, was an effective treatment for local recurrence. Re-irradiation alone failed to control any case with recurrence.

Chronic laryngeal stenosis

The results of treatment of 82 patients with chronic laryngeal stenosis during a 20-year period are presented. Road traffic accidents accounted for 30% of the cases and iatrogenic disease for 40%. Of the stenoses 10% were supraglottic, 20% glottic, 50% subglottic, and 15% combined. Virtually all patients with supraglottic stenosis had a good result as regards voice and airway, and we describe the use of a laryngeal widening operation for this group of patients. Over 80% of patients with glottic stenosis achieved good results. However, patients with a subglottic stenosis did badly, and only 60% were relieved of their tracheostomies. Patients with stenosis due to previous tracheostomy or to systemic disease such as Wegener's granuloma did badly.

Carcinoma in situ of the larynx

A series of 28 cases of carcinoma in situ of the larynx treated over the last 16 years is reviewed. The majority of the patients were treated with endolaryngeal stripping of the cords. In the few cases in which the treatment failed, early detection of disease was made and radiotherapy was successful in controlling the carcinoma. The use of radiotherapy is only advocated for selected cases because there is often difficulty in assessing a radiated larynx; radiotherapy may induce field changes, and if treatment fails, laryngectomy may have to be carried out as a salvage procedure.

Recurrent pleomorphic adenomas of the parotid gland

In this retrospective study of 19 cases of recurrent pleomorphic adenoma of the parotid gland, all 19 patients underwent primary surgery elsewhere, namely, lumpectomy in five cases and superficial parotidectomy in 14 cases. The age at which those patients with recurrence had originally been seen was significantly earlier than those seen in our series of cases of primary surgery for pleomorphic adenoma. If the primary operation had been a parotidectomy, the average time interval between the first and second operation was 7.7 years; however, if it had been a lumpectomy, it was ten months. Implantability of the tumor and inadequate surgery were reasons for tumor recurrence. The suggested treatment of recurrence is total parotidectomy with preservation of the facial nerve. Revision surgery has been successful in all cases with no further recurrences, except in two cases in which multiple operations had already been performed.

The surgical approach to recurrent pleomorphic adenoma of the parotid gland

This is a retrospective study of 19 patients who were referred to the Department of Otolaryngology, Edinburgh Royal Infirmary with recurrent pleomorphic adenoma of the parotid gland. In the majority of patients, a superficial parotidectomy was performed as primary treatment. Recurrence of the tumour was either due to tumour implantation or inadequate surgical excision. Permanent facial paralysis occurred in three patients after revision parotidectomy. Change from pleomorphic adenoma at first operation to carcinoma in pleomorphic adenoma (malignant mixed tumour) at the second was noted in three patients who are still alive and free of recurrent tumour. Eighteen out of the 19 patients did not have further recurrences after revision parotidectomy. The surgical principles in the prevention of tumour recurrence and revision parotidectomy are discussed.