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Biomedical subjects

A Colak

Publications and source records attributed to A Colak.

At least 19 recordsLinked to original sources
PubMed1999

MR imaging for early complications of transpedicular screw fixation.

This series comprises ten patients treated with transpedicular screw fixation, who suffered early postoperative problems such as radicular pain or motor weakness. Besides plain radiographs, all patients were also evaluated with MR imaging. Three patients were reoperated for either repositioning or removal of the screws. MR images, especially T1-weighted ones, were very helpful for visualizing the problem and verifying the positions of the screws. In cases of wide areas of signal void around the screws, the neighboring axial MR images at either side, which have fewer artifacts, gave more information about the screws and the vertebrae.

Adult↗
PubMed1998

The use of near infrared spectroscopy (NIRS) in children after traumatic brain injury: a preliminary report.

Children commonly develop diffuse cerebral swelling after traumatic brain injury (TBI) which is believed due to a secondary response to the injury. Near infrared spectroscopy (NIRS), a continuous, direct, and noninvasive monitor of cerebral oxygenation and cerebral blood volume (CBV), could be helpful in understanding these secondary responses. The aims of our study were to determine whether NIRS used in children with severe TBI will provide insight into the pathophysiology of injury. Ten children (1 mo to 15 years old) with severe TBI (admission GCS < or = 7) were continuously monitored by NIRS by placing optodes over the frontalparietal region. Relative values of oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), and total hemoglobin (THb) were obtained and compared to intracranial pressure (ICP), mean arterial pressure (MAP), electroencephalography (EEG), and arterial PCO2 (PaCO2). Episodes of intracranial hypertension (ICP > 20 Torr [T]), changes in ICP > 10 T, changes in PaCO2 > or = 8 T, and changes in MAP > 20 T frequently resulted in changes in HbO2, Hb, and THb. Hyperventilation with decreased PaCO2 always resulted in cerebral oxygen desaturation irregardless of ICP. Often, high ICP correlated with increased THb and HbO2 indicating increased CBV and cerebrovascular dilatation. In two children, posttraumatic seizures were preceded by an unexplained rapid cerebral hyperoxygenation several hours prior to the onset of the clinical seizures. NIRS reliably detects changes in cerebral hemodynamics in children and may be used to further understand the etiology of the diffuse cerebral swelling seen in children after severe TBI.

Adolescent↗
PubMed1998

Unusual presentation of a sinonasal carcinoma mimicking an aneurysm rupture.

Although the association of subarachnoid hemorrhage (SAH) and tumoral lesions in adult is well known, hemorrhage from a sinonasal carcinoma extending to the intracranial cavity is exceedingly rare. In this paper, the authors report on a 12-year-old girl who presented with SAH caused by a sinonasal carcinoma located in the anterior skull base area. To our knowledge, this is the first report of a sinonasal carcinoma concomitant with SAH.

Aneurysm, Ruptured↗
PubMed1998

Surgical management of spinal cord compression from plexiform neurofibromas in patients with neurofibromatosis 1.

OBJECTIVE: Plexiform neurofibromas with sizable intraspinal extensions and resultant spinal cord compromise pose challenging management problems, because these lesions may involve multiple nerves and engulf adjacent vascular and visceral structures. In this report, we review our experience with the surgical treatment of these lesions. METHODS: Patients were identified by a detailed review of hospital medical records and the database of our multidisciplinary neurofibromatosis clinic. Ten patients had large plexiform neurofibromas that extended intraspinally, producing a combination of myelopathy and radiculopathy. Two patients exhibited single-level intraspinal growth, and eight showed multilevel involvement. Four patients showed bilateral plexiform neurofibromatous growth intraspinally, with "hourglass" compression of the spinal cord. Operative approaches and outcomes were reviewed in detail. RESULTS: Gross total resection of the symptomatic intraspinal tumor component was achieved for nine patients. The management of the extraspinal component was individualized, depending on the pattern and extent of involvement of the surrounding structures. Nine patients experienced complete recovery of neurological function postoperatively; the remaining patient demonstrated significant functional improvement. With a median follow-up period of 4 years, only one patient has developed recurrent intraspinal compression, in this case from tumor involvement by the same plexiform lesion at a lower spinal level. Two patients treated early in the series using standard laminectomy approaches developed significant kyphotic deformities, necessitating subsequent fusion. Based on these initial results, osteoplastic laminotomy techniques were used in the last five cases, allowing anatomic reconstruction of the involved levels; none of these latter patients has developed significant kyphosis, with a median follow-up period of 3 years. CONCLUSION: Radical resection of intraspinal tumor components in patients with neurofibromatosis 1 and large plexiform neurofibromas can help to preserve excellent neurological function. Technical factors in the management of these lesions are presented.

Adolescent↗
PubMed1998

Iatrogenic arachnoid cyst with distinct clinical picture as a result of bone defect in the floor of the middle cranial fossa: case report.

OBJECTIVE AND IMPORTANCE: This kind of arachnoid cyst has not previously been described as a complication of a cranial base bone defect. Recognition of this rare complication may be delayed, because clinicians are unaware of its possibility. CLINICAL PRESENTATION: A 22-year-old man presented with severe headache and increasing difficulty in breathing and swallowing. A physical examination revealed a pulsatile mass in the oral cavity, arising from the parapharyngeal area. A cystic mass that protruded into the oral cavity, through a dural and bony defect in the left middle fossa, was detected on neuroimages. INTERVENTION: A left frontotemporal craniotomy was made, and the cyst was decompressed. Duraplasty was performed with lyophilized dura. The bone defect was managed with a calvarial free bone graft and a pedicled myofacial flap. Serial neuroimaging studies performed postoperatively showed that the cyst had decreased in size. CONCLUSION: This report describes an unusual complication of a cranial base bone defect. Although not all bone defects in the cranial base require reconstruction, management of the large bone defect, particularly in the middle fossa, should preferably be accomplished with the help of a bone graft to support the dural graft.

Adult↗
PubMed1998

An unusual variant of a growing skull fracture in an adolescent.

A great majority of growing skull fractures occur in infancy and earlychildhood. Since the growth of brain is necessary as a driving force for these lesions to occur, almost all reported cases have been before the first 3 years of life. Although a number of uncommon locations, such as basiooccipital and skull base areas, have been reported, they are commonly located on calvaria. The authors report a growing skull fracture on the orbital roof in a 16-year-old female admitted to hospital with complaints of headache and seizures. She had had an orbital trauma 8 years before. CT scan revealed a hypodense lesion in the right frontal lobe and a diastatic fracture line on the right orbital roof. A right craniotomy was performed. Excision of arachnoid loculations and duraplasty were carried out. This is an unusual condition with respect to the location of the lesion, as well as the age of the patient.

Adolescent↗
PubMed1998

Recurrent tethering: a common long-term problem after lipomyelomeningocele repair.

The authors reviewed the records of 94 patients who underwent initial repair of a lipomyelomeningocele between 1982 and July 1996 at the Children's Hospital of Pittsburgh to determine the incidence and time course of symptomatic retethering. In each of these patients, the initial operative goals were to microsurgically debulk as much of the lipoma as possible to allow the conus to move freely within the spinal canal, to divide any tethering arachnoidal adhesions, to close the pia if possible and to reconstitute a capacious thecal sac, using a dural graft if necessary. With a median follow-up of 58 months, 19 of these patients (20.2%) required 28 subsequent operations for symptomatic retethering. Median time between the initial procedure and reoperation for retethering was 52 months. The primary complaint of 12 patients was intractable low-back or leg pain. Other common symptoms were progressive bowel and/or bladder dysfunction, deterioration of motor function and foot deformities. The decision to reoperate was based predominantly on the clinical situation of the patient; magnetic resonance imaging was used to confirm the location and extent of tethering. Patients with transitional lipomas had a significantly higher frequency of symptomatic retethering than those with caudal or dorsal lesions (p < 0.05). No other clinical or technical feature correlated with an increased frequency of retethering. In particular, none of a variety of types of dural graft materials appeared to entirely prevent symptomatic retethering. Following reoperation, pain complaints resolved and many of the other symptoms improved partially or resolved completely. Although the long-term results were also favorable in the majority of patients, a small subgroup (n = 6) exhibited repetitive symptomatic tethering that proved increasingly difficult to treat. We concluded that symptomatic retethering is a common problem in children with lipomyelomeningoceles, even after an adequate initial operation. To date, no type of graft material has been shown to entirely prevent this problem. Close long-term surveillance of such patients is required to allow detection and treatment of symptomatic retethering.

Adolescent↗
PubMed1998

Characterization of microsomal aniline hydroxylase of rainbow trout, Salmo gairdneri.

Aniline hydroxylase from liver microsomes of rainbow trout Salmo gairdneri converted aniline to p-aminophenol, the specific activity being 0.068 nmoles/min/mg protein in potassium phosphate buffer, pH 7.4 at 25 degrees C. The maximal rate of the enzyme reaction was found at aniline concentrations above 5 mM and in the presence of NADPH. Vmax and K(m) were 0.048 nmoles/min/mg and 0.105 mM respectively. The Hill plot showed the Hill constant to be 1.02 indicating one substrate binding site with no cooperativity. Ca2+ and Mg2+ at concentrations ranging between 1-10 mM stimulated the enzyme activity.

Aniline Hydroxylase↗
PubMed1997

A new model for tethered cord syndrome: a biochemical, electrophysiological, and electron microscopic study.

In order to investigate the pathophysiology of the tethered cord syndrome, a few experimental models have been developed and used previously. In this study, the authors present a new experimental model to investigate the biochemical, electrophysiological, and histopathological changes in the tethered spinal cord syndrome. A model was produced in guinea pigs using an application of cyanoacrylate to fixate the filum terminale and the surrounding tissue to the dorsal aspect of the sacrum following 5-gram stretching of the spinal cord. The experiments were performed on 40 animals divided into two groups. The responses to tethering were evaluated with hypoxanthine and lipid peroxidation, somatosensory and motor evoked potentials, and transmission electron microscope examination. The hypoxanthine and lipid peroxidation levels significantly increased, indicating an ischemic injury (p < 0.01). The average hypoxanthine level in the control group was 478.8 +/- 68.8 nmol/g wet tissue, while it was 651.2 +/- 71.5 nmol/g in the tethered cord group. The lipid peroxidation level in group I was 64.0 +/- 5.7 nmol/g wet tissue, whereas it was 84.0 +/- 4.7 nmol/g in group II. In the tethered cord group, the latencies of the somatosensory and motor evoked potentials significantly increased, and the amplitudes decreased. These changes indicated a defective conduction in the motor and sensorial nerve fibers. In the transmission electron microscopic examinations, besides the reversible changes like edema and destruction in the gray-white matter junction, irreversible changes like scarcity of neurofilaments and destruction in axons and damage in myelin sheaths were observed. We consider that this work can be used as an experimental model for tethered cord syndrome.

Animals↗
PubMed1997

Follow-up of children with shunted hydrocephalus.

In order to determine if routine yearly evaluations of children with shunted hydrocephalus were likely to diagnose shunt malfunction, we reviewed the medical records of the last 100 children who had such routine evaluations. Only 4 children had symptoms that were potentially referable to malfunction; none were subsequently found to have malfunction and no child had signs of malfunction. We also reviewed the medical records of the last 100 children who had shunt revisions to determine if any of them were diagnosed during routine follow-up examinations. Four were: 2 with clinical signs of malfunction and 2 with evidence of malfunction on routine scans. Only 1 child in either group had signs or symptoms of malfunction if they had a functioning shunt in place for longer than 1 year. Although yearly follow-up visits are common practice, we conclude that such examinations are unlikely to detect shunt malfunction. Follow-up at intervals of 2 years is probably appropriate after 2 years of age if the child has had a functional shunt for 1 year and has had a scan that indicates a functioning shunt.

Child↗
PubMed1996

Effect of divalent metal ions on the microsomal aniline hydroxylase system of rainbow trout.

The ability of trout to metabolize aniline in vitro in the presence of some divalent metal ions was investigated in the liver microsomes of rainbow trout, Salmo gairdneri. Trout liver microsomes were highly capable of catalyzing aniline hydroxylation to p-aminophenol with a specific activity of 0.068 nmoles/ min per mg of microsomal protein in potassium phosphate buffer, pH 7.4 at 25 degrees C. The activity of the aniline hydroxylase system was competitively inhibited by Hg+2, Ni+2, Cd+2, and Zn+2, while Cu+2 and Fe+3 seemed to inhibit the activity noncompetitively at 1 mM aniline concentrations. IC50 values at fixed aniline concentration were estimated to be 0.45 mM for Hg+2, Ni+2, and Cd+2, 1.8 mM for Zn+2 and Fe+3, and 1.3 mM for Cu+2. Eadie-Hofstee plots gave identical Vmax values of approximately 0.046 nmol/min per mg of protein while K(m) values were increased in the presence of Hg+2, Ni+2, Cd+2, and Zn+2, indicating competitive inhibition. Both K(m) and Vmax values were affected by Fe+3 and Cu+2, suggesting noncompetitive inhibition. Ki values extracted from the Dixon plots were determined to be 0.23, 0.43, and 0.65 mM for Hg+2, Ni+2, and Cd+2, respectively, providing the most effective inhibition on the aniline hydroxylase system among studied metal ions. The Ki values were much higher in the presence of others. The results indicate a selective inhibition of the aniline hydroxylase system of trout liver microsomes by divalent metal ions.

Aniline Hydroxylase↗
PubMed1996

CNS involvement of Langerhans cell histiocytosis. Report of 23 surgically treated cases.

We present 23 cases of Langerhans cell histiocytosis with central nervous system (CNS) involvement. The major complaints were a mass on the cranial vault in fifteen (65%), visual disturbance in four (16%), polyurea-polydipsia in three (13%), and progressive weakness in all extremities in one patient (4%). Neurological examination revealed no abnormality in sixteen patients (70%), cranial nerve palsy, visual field defect and optic atrophy in six (26%) and paraparesis in one (4%). Tumoral mass was found to be located on the cranial vault (65%), in the suprasellar region (21%) and in the spinal column (8%). The cranium and spinal column were both involved in one patient. All patients underwent surgery; craniectomy with grossly total tumor excision plus cranioplasty (65%), craniotomy with subtotal tumor excision (26%), and vertebrectomy with grafting (13%) were performed. The clinical, radiological and histopathological features, as well as therapeutical considerations are discussed and the pertinent literature is reviewed.

Adolescent↗
PubMed1996

A huge cerebral hydatid cyst associated with small liver cyst: a comparison of growth rates and sizes.

There are still some unknown aspects of the natural course of echinococcus infestation, especially in the brain. The growth rate of the cysts in brain and in other tissues is matter of some discussion. In this report, a huge primary cerebral hydatid cyst associated with a small liver cyst is presented and a possible relationship between the growth rates and the sizes of the two cysts is discussed. It is shown that the brain hydatid cyst grew faster than liver hydatid cyst by a ratio of 3:1.

Antinematodal Agents↗