technetium-tc-99m-exametazime and Arachnoid-Cysts

Many arachnoid cysts (AC) are detected incidentally in asymptomatic patients. Current neuroimaging methods provide only morphological details of the cysts, but they do not give information about cerebral function. While surgery is indicated in symptomatic patients, the management of asymptomatic individuals, who present with large cysts, is controversial.. To ascertain the value of cerebral 99 mTc-HMPAO single photon emission computed tomography (SPECT) for detecting brain dysfunction in cases of intracranial ACs, aimed at allocating the patients for surgical or for conservative treatment.. We studied prospectively 11 patients diagnosed with sylvian fissure ACs. The subjects underwent neurological examination, EEG, neuroimaging studies, neuropsychological testing, and cerebral perfusion studies with 99 mTc-HMPAO SPECT.. The patients' ages ranged from 2 to 42 years (median 16 years). The study group consisted of ten symptomatic patients with ACs and one patient with an incidental cyst. Seven patients showed diminished regional cerebral blood flow (rCBF) in their initial cerebral SPECT. Four individuals underwent surgery. Seven patients showed normalization of rCBF after surgical or conservative treatment.. Cerebral SPECT demonstrated impaired brain perfusion in 70% of symptomatic patients. The zone of decreased rCBF corresponded well with clinical symptoms and with neuroimaging findings. Patients exhibiting normal rCBF in SPECT studies remained or became asymptomatic during the follow-up time. Cerebral SPECT constitutes a valuable adjunct tool for correlating regional function with brain anatomy, and may be of help to allocate patients with ACs for surgical treatment or clinical observation. Further research on this field is warranted.

Topics: Adolescent; Adult; Arachnoid Cysts; Brain; Cerebrovascular Circulation; Child; Child, Preschool; Electroencephalography; Female; Humans; Infant; Magnetic Resonance Imaging; Male; Neurologic Examination; Neuropsychological Tests; Patient Selection; Postoperative Complications; Prognosis; Regional Blood Flow; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Three children with middle fossa arachnoid cysts, presenting with non-specific symptoms and otherwise well, were investigated before and after surgery with magnetic resonance and 99Tc-hexamethylpropyleneamineoxime single photon emission computerised tomography scans, to assess the effect of the cysts on cerebral blood flow. All patients had evidence of a reduction in cerebral blood flow at presentation, even in the hemisphere contralateral to the middle fossa cyst, implied by perfusion defects seen centrally in the deep white matter of both cerebral hemispheres. After successful surgical excision of the cyst, the perfusion defects disappeared. This was associated with general improvement of pre-existing non-specific symptoms. These findings indicate that middle fossa arachnoid cysts may cause global impairment of brain function by interfering with its blood supply. This does not support the generally held view that such cysts are benign in nature when 'asymptomatic'.

Topics: Adolescent; Arachnoid Cysts; Brain Ischemia; Child, Preschool; Dominance, Cerebral; Humans; Magnetic Resonance Imaging; Male; Postoperative Complications; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

The progression of congenital arachnoid cysts has seldom been documented. We report the case of a child who was diagnosed with arrested hydrocephalus at the age of 13 months. Neuroimaging studies performed when the girl was 22 months old showed the appearance of an arachnoid cyst in the right middle fossa, while the previously enlarged ventricles seemed to have decreased in size. To the best of our knowledge, the paradoxical expansion of an arachnoid pouch following a reduction in the size of the ventricular system has not previously been documented. We advance the hypothesis that the development of some cases of arachnoid cyst might be pathogenically related to impaired CSF dynamics associated with pre-existing hydrocephalus. We also briefly review the pertinent literature on the formation and evolution of congenital cerebral arachnoid cysts.

Topics: Arachnoid Cysts; Cerebrospinal Fluid Pressure; Cerebrospinal Fluid Shunts; Child; Child, Preschool; Female; Follow-Up Studies; Humans; Hydrocephalus; Infant; Magnetic Resonance Imaging; Peritoneum; Recurrence; Reoperation; Technetium Tc 99m Exametazime; Temporal Lobe; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed; Treatment Outcome; Wechsler Scales

A method for registering three-dimensional CT, MR, and PET data sets that require no special patient immobilization or other precise positioning measures was adapted to high-resolution SPECT and MRI and was applied in 14 subjects (five normal volunteers, four patients with dementia (Alzheimer's disease), two patients with recurrent glioblastoma, and three patients with focal lesions (stroke, arachnoid cyst and head trauma]. T2-weighted axial magnetic resonance images and transaxial 99mTc-HMPAO and 201Tl images acquired with an annular gamma camera were merged using an objective registration (translation, rotation and rescaling) program. In the normal subjects and patients with dementia and focal lesions, focal areas of high uptake corresponded to gray matter structures. Focal lesions observed on MRI corresponded to perfusion defects on SPECT. In the patients who had undergone surgical resection of glioblastoma followed by interstitial brachytherapy, increased 201Tl corresponding to recurrent tumor could be localized from the superimposed images. The method was evaluated by measuring the residuals in all subjects and translational errors due to superimposition of deep structures in the 12 subjects with normal thalamic anatomy and 99mTc-HMPAO uptake. This method for superimposing magnetic resonance and high-resolution SPECT images of the brain is a useful technique for correlating regional function with brain anatomy.

Topics: Alzheimer Disease; Arachnoid Cysts; Brain; Brain Injuries; Cerebrovascular Disorders; Glioma; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Organotechnetium Compounds; Oximes; Technetium Tc 99m Exametazime; Thallium Radioisotopes; Tomography, Emission-Computed, Single-Photon