Preventing damage to miniature-loudspeaker by means of dynamic detection of excessive diaphragm displacement.

The rapid development of consumer electronics and the extensive use of mobile devices require the ample use of miniature-loudspeakers for audio applications. The demand for better sound pushes manufacturers to design digital signal processing (DSP) chips (smart amplifiers), which in turn could cause unpleasant sound due to distortion and parameter nonlinearity or transducer damage caused by large diaphragm excursion or voice-coil (VC) burn. This article presents a methodology for nonlinear parameter estimation using an inverse method and displacement limiter for large VC displacement-dependent transducer damage prevention. A set of transduction equations is employed to inversely determine parameters using a polynomial expression. The appropriate selection of an objective function incorporating the unknown vector of nonlinear parameters leads to the adjoint problem that requires a gradient solution. A numerical solver is provided to obtain the VC displacement, current, and derivatives using a robust hybrid spline differential method. The dynamic limiter is proposed to control the peak values of the VC velocity so as to limit an excessive displacement which prevents impulsive damage to the receiver and further application of the DSP board. Numerical and experimental results indicate that the proposed method has high efficiency and can be widely used in transducer applications.

Preparation and thermal studies on tetranitrodibenzo tetraazapentalene (TACOT): a thermally stable high explosive.

Thermally stable high explosive, tetranitro-2,3,5,6-dibenzo-1,3a,4,6a-tetraazapentalene (TACOT) was synthesized and characterized during this work. Thermo analytical techniques (TG and DSC) were applied to study the thermal decomposition behaviour of TACOT in comparison with benchmark thermally stable high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Kinetic parameters such as reaction order, activation energy and pre-exponential factors were computed from the thermal data. The activation energy for TACOT (292 kJ/mol) was found 1.5 times to that of TATB (200 kJ/mol), which can account for its higher thermal stability and can be attributed to pentalene moiety in the former.

Synthesis, characterization and thermolysis studies on triazole and tetrazole based high nitrogen content high energy materials.

This paper reports the synthesis, characterisation and thermolysis studies of hydrazinium azotetrazolate (HAZ) and 1,1'-dinitro-3,3'-azo-1,2,4-triazole (N-DNAT). TGA and DSC results suggested that HAZ decomposes in the range of 150-180 degrees C and N-DNAT in the range of 160-170 degrees C, respectively. The pattern of decomposition of HAZ dihydrate and N-DNAT has been predicted with the help of pyrolysis GC/MS technique and a probable decomposition mechanism has been proposed. The theoretically predicted performance data suggests the potential nature of HAZ and N-DNAT for their use in propellant/explosive as well as in gas generator formulations.

CT stereotaxy guided lateral trans-cerebellar programmable fourth ventriculo-peritoneal shunting for symptomatic trapped fourth ventricle.

A trapped fourth ventricle is a rare clinico-radiological entity producing symptoms suggestive of a progressive posterior fossa mass lesion. It is mainly reported in children as a late complication of lateral ventricular shunting to relieve infantile post-meningitic or post-hemorrhagic hydrocephalus. Optional treatment of the trapped fourth ventricle remains controversial. Placement of fourth ventricular shunting via a conventional midline approach can be fraught with complications in about 40% of the patients. Authors report a successful CT Stereotaxy guided high pressure (80 mm H(2)O) programmable fourth ventriculo-peritoneal shunting via a lateral trans-cerebellar approach in a 14-year-old girl with a trapped fourth ventricle, which occurred as a late complication of ventriculo-peritoneal shunting in her infancy. Her preoperative symptoms of raised intracranial pressure, bobble-head doll syndrome and bilateral abducens palsies completely improved following the surgery. Lateral trans-cerebellar stereotactic placement of the fourth ventricular catheter and the use of high-pressure (low flow) programmable shunt (to avoid complications associated with over drainage) are beneficial in some patients with trapped fourth ventricle.

Frontal intraosseous cryptic hemangioma presenting with supraorbital neuralgia.

Primary intraosseous cranial hemangiomas are rare benign tumors comprising 0.2% of all osseous neoplasms. Symptomatic cranial cryptic hemangiomas are extremely rare. We report the case of a 43-year-old man with a cryptic hemangioma of the superior orbital rim. Radiological investigations revealed it to be an intraosseous cryptic mass which was totally excised and the supraorbital nerve was decompressed, relieving the patient of his symptoms. Histopathology showed features of an intraosseous hemangioma.

Endodermal cyst of septum pellucidum and pregnancy: a case report.

BACKGROUND: Endodermal or Neurenteric cysts are commonly found in spine. Their intracranial occurrence is rare and such a cyst in the septum pellucidum is exceptional. METHOD: We report a woman, with 33 week pregnancy, presenting in a semiconscious state due to raised intracranial pressure (ICP) due to hydrocephalus caused by a large lesion in the septum pellucidum. Computed tomography (CT) revealed the lesion which was better characterised by the Magnetic Resonance Imaging (MRI). First baby was delivered by LSCS and bilateral ventriculo-peritoneal shunts were inserted; and later on the cyst was excised. RESULT: There was full neurological recovery following the insertion of VP shunt. After excision of cyst cerebrospinal fluid (CSF) pathway was established and shunts could be removed. Post-operative period was complicated by septic ventriculitis. Eventually patient was discharged home in excellent condition. CONCLUSION: Endodermal cyst of septum pellucidum is an uncommon condition. Such lesions may be large when revealed, good outcome is expected after surgical excision.

Schwannoma of the suprascapular nerve presenting with atypical neuralgia: case report and review of the literature.

Compressive lesions of the suprascapular nerve produce weakness and atrophy of the supra- and infraspinatus muscles and a poorly defined aching pain along the posterior aspect of the shoulder joint and the adjacent scapula. Entrapment neuropathy of the suprascapular nerve is fairly common whereas tumorous lesions are rare; among the latter ganglion cysts are frequently seen. An isolated solitary schwannoma of the suprascapular nerve presenting with atypical neuralgic pain is exceptional. The location of a schwannoma under the firm deep cervical fascia in the posterior triangle of the neck is implicated in the genesis of neuralgic pains mimicking the suprascapular entrapment syndrome. One such case is reported with discussion of the relevant clinical features.

Primary orbito-cranial adenoid cystic carcinoma with torcular metastasis: a case report and review of the literature.

Adenoid cystic carcinoma is a rare neoplasm arising from the exocrine glands such as salivary glands, lachrymal glands, upper respiratory tract, breast or uterine cervix. Intracranial involvement is commonly from direct skull base involvement, although metastasis may rarely be seen. The predisposition of the adenoid cystic carcinoma for perineural and perivascular invasion is the prime reason for the locally invasive character of the tumour, often extending into the cranium via foramina at the skull base. The authors report a case of primary orbito-cranial extradural adenoid cystic carcinoma and cranial metastasis away from the primary site. This patient initially had a local excision, and later an exenteration of the right eye followed by with radiotherapy. Within months she presented with an extradural cranial recurrence, distant torcular metastasis without any neurological deficit. Craniotomy and radical excision was undertaken as these tumours have slow growth rates, and long term survival of the se patients even in the presence of local recurrence and metastasis has been well documented.

Symptomatic epineural ganglion cyst of the ulnar nerve in the cubital tunnel: a case report and brief review of the literature.

An unusual case of pain and weakness in the hand and forearm due to a ganglion cyst of the ulnar nerve at the elbow is presented. The patient was managed initially as a case of cervical disc disease and cervical spondylosis and later as a case of carpal tunnel syndrome at an another institution. Cervical radiography and cervical magnetic resonance imaging scans were inconclusive. Neurosurgical referral revealed tenderness at the right cubital tunnel, weakness of the right hand and forearm muscles, and sensory deficit along the medial border of the forearm and the hand. The diagnosis of ulnar nerve compression at the elbow was made. Nerve conduction studies of the ulnar nerve at the elbow confirmed the diagnosis. A ganglion cyst of the ulnar nerve was excised microsurgically with a complete postoperative sensory motor recovery.

Symptomatic ependymal cysts of the perimesencephalic and cerebello-pontine angle cisterns.

Primary intracranial ependymal cysts are extremely rare. These are congenital, benign ependyma lined, commonly intraparenchymal and uncommonly extraparenchymal cysts in leptomeningeal location of variable size seen in the adult life. The authors report two cases of symptomatic ependymal cysts: one in the perimesencephalic cistern in a 10-month-old infant presenting with delayed mile stones and another in the cerebello-pontine cistern in a morbidly obese 35-year-old woman with known benign intracranial hypertension now presenting with hemifacial spasm. Neurosurgical intervention was curative in both cases. Interesting clinical, radiological and histological features are presented and discussed.

Pharyngeal perforation and spontaneous extrusion of the cervical graft with its fixation device: a late complication of C2-C3 fusion via anterior approach.

Stabilisation of the fracture-dislocation of the cervical spine is achieved effectively by anterior or posterior or combined methods with attendant short and long term benefits, risks and complications associated with each procedure. Recently anterior methods have gained wider acceptance. A variety of preoperative and postoperative complications associated with anterior cervical fusion are well recognised. However, the delayed pharyngeal or oesophageal perforation is a rare, serious and life threatening complication of an anterior cervical internal fusion.The authors report a case of delayed pharyngeal perforation and spontaneous extrusion of the C2-C3 graft with its fixation device. After coughing out the entire gamet of the graft with the fixation pin, the patient was relieved of excruciating pain and dysphagia and had no significant morbidity thereafter over a 12-year follow up period. Relevant aspects are discussed with a review of the pertinent literature.

Vagal schwannoma of the cerebello-medullary cistern presenting with hoarseness and intractable tinnitus: a rare case of intra-operative bradycardia and cardiac asystole.

Schwannomas arising from the lower cranial nerves (IX-XI) are rare, constituting only 3% of all intracranial schwannomas unassociated with neurofibromatosis. A great majority of these tumours present as jugular foramen lesions and less commonly they occur along the extracranial course of these nerves. An intracisternal location is extremely rare. We report a case of vagal schwannoma purely in the cerebello-medullary cistern causing distortion of the medulla oblongata. Total microsurgical excision of this tumor, arising from one of the rootlets of the vagus nerve, was achieved with preservation of the 9th, 10th and 11th cranial nerves.The intraoperative course was complicated by two episodes of complete cardiac asystole, each lasting for 4(s), and six episodes of severe bradycardia. The patient was relieved of his intractable tinnitus but continued to have a hoarse voice due to an ipsilateral partial vocal cord palsy.

Fatal rhino-orbito-cerebral mucormycosis in an apparently normal host: case report and literature review.

Fungal infections of the central nervous system (CNS) are fortunately rare but remain challenging problems occurring mostly in immunocompromised individuals, with protean manifestations, unpredictable course and unfavorable outcome in many cases despite aggressive neurosurgical intervention and recent antifungal drugs. Rhino-orbito-cerebral mucormycosis is a potentially lethal opportunistic fungal infection with rapid progression and high mortality. Its pathogenic nature becomes evident when the patient's general resistance is compromised. We present a case of an invasive rhino-orbito-cerebral mucormycosis in an apparently normal adult who initially developed mild paranasal sinusitis and later developed status epilepticus and despite an aggressive management died. Interesting clinical, neuroimaging and histological findings are described, and the possibility of fatal mucormycosis in an apparently normal host is highlighted.

Cranio-spinal enterogenous cysts: clinico-radiological analysis in a series of ten cases.

Enterogenous cysts are rare congenital lesions resulting from dysgenesis during the third embryonic week at the time of notochord development and the transitory existence of the neurenteric canal. Enterogenous cysts are usually lined by mucus secreting epithelium resembling that of the gastrointestinal tract. The inclusion of the endodermal elements in the spinal canal may produce extradural, intradural extramedullary or intradural intramedullary cystic lesions. The endodermal inclusions producing cysts in the intracranial compartment are extremely rare, especially in the supratentorial region. Plain X-rays may show concomitant cranio-spinal anomalies. However, CT and MRI scans show better definition and characterisation. Total excision is the procedure of choice in these benign cysts with favourable long term prognosis. Approximately 100 histologically proven cases have been described, with a few exceptions, as isolated case reports the authors report a detailed analysis of the clinico-radiological aspects of a series of ten patients with cranio-spinal enterogenous cysts with a review of the literature.

Congenital and late-onset primary haemangiomas of the temporalis muscle: case report.

We report on two patients with haemangiomas of the temporalis muscle, one congenital and one of late onset, which were diagnosed on computed tomography. Both were resected successfully and both patients are well with no signs of recurrence 3(1/2) years and 18 months later, respectively.

Choroid plexus papilloma of the posterior third ventricle during infancy & childhood: report of two cases with management morbidities.

We report two cases of posterior third ventricular choroid plexus papilloma, one in an 8-month-old infant and another in a two-year-old child. These cases presented with features of obstructive hydrocephalus. Both these patients underwent a ventriculo-peritoneal (VP) shunt surgery prior to the tumor excision. Following the VP shunt surgery both patients developed ascitis requiring exteriorization of the abdominal end of the shunt. There was a clear proof of CSF overproduction: 1400-1500 ml/day in the eight-month-old infant and 900-1200 ml/day in the two-year-old child. In the former it was transient and could be treated with revision of the VP shunt whereas in the second case a ventriculo-arterial shunt had to be done. In the second case a staged reduction cranioplasty was also performed for an enormously enlarged head (head circumference--74 cm). Interesting clinical and radiological findings and useful management strategies are described.

Sudden bilateral foot drop: an unusual presentation of lumbar disc prolapse.

Bilateral acute foot drop is reported in a 30-year-old healthy male. He presented with a 7-day history of sudden severe backache, radiating to both the lower limbs and 1-day history of sudden bilateral ankle weakness that progressed to bilateral foot drop within 6 hours. He also developed retention of urine. Investigations revealed a large central disc prolapse at L3-4 with significant canal stenosis at that level. Following surgery the patient had progressive improvement.

Gluteal neuralgia - unusual presentation in an adult with intrasacral meningocele: a case report and review of literature.

A nineteen year old man with intrasacral meningocele is reported, who presented with long standing episodic gluteal pain and progressive muscle wasting. Magnetic resonance imaging established the diagnosis. Surgical excision relieved the pain but muscle wasting persisted. Pertinent literature is reviewed.

Spinal cord and cauda equina compression in 'DISH'.

Diffuse idiopathic skeletal hyperostosis (DISH) has long been regarded as a benign asymptomatic clinical entity with an innocuous clinical course. Precise information is lacking in the world literature. Authors report the results of a retrospective analysis of 74 cases of DISH. Eleven patients presented with progressive spinal cord or cauda equina compression. In nine cases ossified posterior longitudinal ligament (OPLL) and in two cases ossified ligamentum flavum (OLF) were primarily responsible. Surgically treated patients (eight) had far better outcome as compared to the patients managed conservatively, as they had refused surgery. 'DISH' is neither a benign condition, nor it always runs a innocuous clinical course. In fact, in about 15% of the cases, serious neurological manifestations occur, which may require a major neurosurgical intervention.

Sciatica due to malignant nerve sheath tumour of sciatic nerve in the thigh.

Malignant peripheral nerve sheath tumour (MPNST) is a rare malignant neoplasm arising from the supportive non-neural component of the peripheral nerves. An unusual case of pain and weakness of the foot and calf muscles due to a giant MPNST of the sciatic nerve in the posterior compartment of the thigh is presented. The patient was already investigated as a case of sciatica due to a lumbar disc disease with a negative magnetic resonance imaging and then unsuccessfully operated elsewhere twice, with a misdiagnosis of tarsal tunnel syndrome. Neurosurgical referral prompted a diagnostic magnetic resonance study of the thigh, revealing the lesion, which was completely excised microsurgically with total relief in the pain and partial improvement in the weakness and sensations in the sole of the foot.