Anatomy of the visual system.

This brief systemic overview presents the anatomic details of the orbit with respect to imaging modalities CT and MR. The structures of the four orbital compartments, intrakonal and extrakonal space, globe and optic nerve are demonstrated in detail on different CT and MR views (axial, coronal, in soft tissue and bone window, T1-weighted, T2-weighted) with corresponding diagrams. The intracranial visual pathway is explained in detail with emphasis to the striate cortex and extrastriate visual association cortex, presented with diagrams and high-resolution MR.

[Palliative treatment of brain metastases with gamma knife]. / Palliative Behandlung von Hirnmetastasen mit dem Gamma Knife.

The gamma knife is a stereotactic radiosurgery device which allows well defined, deep seated brain tumors or arteriovenous malformations with a maximal volume of about 25 ccm and a diameter not greater than 3.5 cm, to be treated in a single session under local anesthesia. The gamma knife offers an alternative treatment method to the classical approach of treating brain metastases by surgical excision and/or whole brain radiotherapy. The advantages of this technique are evident: the method is non-invasive, the treatment is carried out in a single session with a very short hospitalisation of two to three days, it is exempt from physical and psychical stress, the head does not need to be shaved and no hair loss occurs, a good quality of life is obtained for a reasonably prolonged survival time and it offers an economically favourable treatment method. Up to December 1999, over 30,000 patients suffering from brain metastases have been treated worldwide using the gamma knife. In Zürich, from September 1994 to December 2000 140 received this treatment. In the literature selection criteria may differ, and this may have determined some of differences in outcome. However, our results are comparable with those in the majority of publications with an average survival time of 263 days and a maximum survival of 1080 days. Good prognostic factors for survival and local control of brain metastases are a Karnofsky Performance Scale Score approaching 90 to 100, but not lower than 70, tumour volume, controlled primary cancer, and absence or stable extracranial metastases.

Worst-Fechner biconcave minus power phakic iris-claw lens.

OBJECTIVE: Evaluation of long-term results of correction of high myopia by implantation of a biconcave Worst-Fechner minus power iris-claw lens into phakic eyes. METHODS: One hundred and twenty-seven eyes of 70 patients were implanted with the phakic IOL between November 1986 and November 1991. The mean preoperative spherical equivalent refraction was -14.29 +/- 5.77 D (range -5.00 to -31.75 D). The total population decreased from 127 to 68 eyes (53.5%) at the 8-year examination. By this time, 26 of the 70 patients (37%) had been lost to follow-up for unknown reasons. Corneal endothelial density was estimated by comparing the image gained by non-contact specular microscopy with a graduated reticule (Karickhoff method). RESULTS: At the 6-month examination, mean deviation of achieved from calculated refractive correction was +0.52 +/- 1.46 D (range -2.25 to +6.50 D). Seventy-seven eyes (62.1%) deviated 1.00 D or less, and 15 eyes (12.1%) deviated by more than 2.00 D from the calculated correction. A refractive outcome of +/- 1.00 D was attempted in 68 eyes (54% of the 124 eyes) and was achieved in 51 eyes (75%). Mean spectacle-corrected visual acuity preoperatively was 0.54 +/- 0.27 (range 1.20 to 0.05). At the 6-month examination it was 0.73 +/- 0.3, and by the 8-year examination had decreased to 0.65 +/- 0.26. Statistical analysis of corneal endothelial cell density revealed a significant correlation of endothelial cell loss with age (> or = 45 years), anterior chamber depth (< or = 3.4 mm), and IOL power (> or = -11.00 D). Seventeen eyes (13.4%) had a decrease in endothelial cell density and projection to 8-year follow-up resulted in a decrease in 27% of eyes. Four eyes needed a penetrating keratoplasty. CONCLUSION: Implantation of a biconcave Worst-Fechner lens into a phakic eye effectively corrected high myopia with a stable refractive outcome, but 13.4% of implanted eyes suffered significant progressive reduction of endothelial cell density. This style lens is no longer in clinical use.

3D T2-weighted fast spin-echo MRI sialography of the parotid gland.

The diagnostic value of 3D T2-weighted MRI sialography and 2D T2-weighted fast spin-echo (FSE) images for delineation of the normal duct system and characterisation of parotid gland duct pathology was compared in a prospective study. We studied eight healthy volunteers and 18 patients with pathology of the parotid gland (tumours in 3, sialolithiasis in 6, Sjögren's disease in 4, recurrent or chronic parotitis in 4, post-traumatic stricture of the main parotid duct in 1). A heavily T2-weighted 3D FSE sequence was compared with a conventional 2D T2-weighted FSE sequence. The normal main parotid duct was always visible on 3D sialography and seen in 68% of the 2D T2-weighted FSE studies. The diagnostic reliability of both sequences for diagnosis of luminal concretions in sialolithiasis and dilatation of the duct in duct stricture or chronic parotitis was equal, although slight intraglandular dilatation was appreciated only on 3D sialography. Extraductal pathology resulting in obstruction or displacement of ducts was better characterised on 2D T2-weighted images. However, 3D MRI sialography offered the advantage of postprocessing with overview images and multiple maximum-intensity projection images in any plane.

Extradural vertebral artery dissecting aneurysm causing subarachnoid haemorrhage.

The authors report the case of a 37-year-old man who presented with subarachnoid haemorrhage (SAH) after rupture of an extradural vertebral artery dissecting aneurysm. The patient underwent a left lateral suboccipital craniotomy with removal of the medial part of the occipital condyle and the fusiform dilatation was coated. The angiograms 3 months after surgery showed aneurysm resolution and normal vessel calibre. To the authors' knowledge, it is the second reported case of extracranial vertebral aneurysm of its kind presenting as SAH. The result after surgery in this case indicates that coating of a dissecting aneurysm of the extracranial portion of the vertebral artery (VA) is a valid alternative surgical technique for the prevention of rebleeding.

T2-weighted three-dimensional fast spin-echo MR in inflammatory peripheral facial nerve palsy.

PURPOSE: Our objective was to identify histologically and intraoperatively verified focal nerve thickening of the distal intrameatal segment on three-dimensional fast spin-echo (FSE) T2-weighted MR images as a new diagnostic criterion in patients with inflammatory peripheral facial nerve palsy. METHODS: Twenty-two patients with clinically diagnosed unilateral (n = 20) or bilateral (n = 2) inflammatory peripheral facial nerve palsy were examined on a 1.5-T MR imager using noncontrast and contrast-enhanced T1-weighted SE sequences and 3-D T2-weighted FSE sequences with secondary reformations. Abnormal contrast enhancement and possible focal nerve thickening of the distal intrameatal segment, labyrinthine nerve segment, and geniculate ganglion region were analyzed prospectively. RESULTS: In all patients, the T1-weighted postcontrast SE images showed characteristic smooth, linear, abnormally intense contrast enhancement of the distal intrameatal segment, indicating peripheral inflammatory nerve palsy. In 23 nerves (96%) a focal bulbous nerve thickening of the distal intrameatal segment was observed on 3-D T2-weighted FSE images. In 100% of patients with peripheral inflammatory facial nerve palsy, postcontrast T1-weighted SE images showed a smooth, linear, and abnormally intense contrast enhancement of the distal intrameatal segment; reformatted very thin 3-D T2-weighted FSE images showed a focal bulbous nerve thickening of the distal intrameatal segment in 96% of patients. These findings corresponded to intraoperative and histologic findings. CONCLUSION: Three-dimensional T2-weighted FSE sequences are fast and cheap compared with T1-weighted postcontrast images, but secondary reformations are time-consuming and require exact anatomic knowledge for careful analysis of the different nerve segments.

Escher-Hirt syndrome.

A mother and her two daughters are reported with bilateral conductive deafness due to incudo-stapedial abnormalities, and microtia with thickened ear lobes. This pattern of abnormal findings, transmitted with an autosomal dominant mode of inheritance, is characteristic of the Escher-Hirt syndrome. One of the daughters died from an additional cardiac malformation (VSD). Anomalies of the middle ear were demonstrated in the surviving patients by computed tomography. Differential diagnosis with other genetic syndromes associated with deafness, and possible therapeutic approaches are discussed.

Contrast-enhanced MR of the facial nerve in patients with posttraumatic peripheral facial nerve palsy.

PURPOSE: To estimate the value of noncontrast and contrast-enhanced T1-weighted MR imaging in detecting the underlying mechanisms of injury and regeneration in immediate- or delayed-onset posttraumatic peripheral facial nerve palsy. METHODS: Twenty-four patients with posttraumatic peripheral facial nerve palsy were examined on a 1.5-T MR imaging unit with precontrast and postcontrast T1-weighted spin-echo and gradient-echo sequences. RESULTS: Abnormal enhancement of the distal intrameatal nerve segment was visible in 92% of the patients up to 2 years after their initial trauma. A hematoma within the geniculate ganglion was seen in 33% of the patients with a longitudinal fracture. The greater superficial petrosal nerve (in 32% of patients) and the geniculate ganglion (in 48% of patients) were thick and intensely enhancing. Hematoma within the cochlea/vestibule or enhancement of the cochlea/vestibule and the vestibulocochlear (eighth) nerve was observed in transverse fractures. CONCLUSION: MR images can show long-lasting abnormal nerve enhancement, especially in the distal intrameatal nerve segment, related to the long-lasting breakdown of the blood/peripheral nerve barrier associated with nerve degeneration and regeneration after traumatic stretching of the greater superficial petrosal nerve. Additionally, intraoperatively observed perineural and intraneural scar formation leads to thickening and intense enhancement of the affected nerve segments on MR images. A hematoma in the region of the geniculate ganglion can be seen in some but not all patients. Associated damage of the inner ear structures in patients with transverse fractures is also visible on MR images.

Aneurysm clips made of titanium: magnetic characteristics and artifacts in MR.

PURPOSE: To evaluate the magnetic characteristics, artifact formation, and implant safety of titanium aneurysm clips for use in MR imaging. METHODS: Aneurysm clips made of titanium alloy TiAl6V4 were tested in a magnetometer to determine their magnetic susceptibility and in a 1.5-T MR imager using both a geometric phantom and an animal model. A commercially available alpha-Phynox clip served as the reference standard. RESULTS: We found minimal magnetization and a significant reduction in image artifacts with the titanium clip as compared with the Phynox clip. CONCLUSION: The titanium clips improve image quality, biocompatibility, and patient safety in medical MR applications.

MR differentiation of adamantinous and squamous-papillary craniopharyngiomas.

PURPOSE: To determine MR criteria for differentiating adamantinous from squamous-papillary craniopharyngiomas. METHODS: The MR imaging features of 42 histologically proved craniopharyngiomas (25 adamantinous, 15 squamous-papillary, and two mixed subtypes) were examined with multiplanar T2-weighted and noncontrast and contrast-enhanced T1-weighted imaging. Differences in the mR features of both subtypes were evaluated retrospectively. RESULTS: The adamantinous craniopharyngioma is a mixed solid-cystic or mainly cystic lobulated suprasellar or intrasellar/suprasellar tumor occurring in children and adults, typically with large nonenhancing hyperintense cysts on T1-weighted images. The squamous-papillary craniopharyngioma is a predominantly solid or mixed solid-cystic suprasellar tumor occurring in adults, appearing as a hypointense cyst on noncontrast T1-weighted images. Calcifications and recurrent tumors are more often observed in adamantinous tumors but can be seen in squamous-papillary tumors as well. Statistically significant parameters useful for differentiating the two tumor subtypes are the encasement of vessels, the lobulated shape, and the presence of hyperintense cysts in adamantinous tumors, and the round shape, the presence of hypointense cysts, and the predominantly solid appearance in squamous-papillary tumors. CONCLUSION: Craniopharyngiomas can be divided into two clinically, histologically different subtypes, which suggests a different pathogenesis of these two types of tumor.

Spinal MRI in vacuolar myelopathy, and correlation with histopathological findings.

We correlated MRI features with histopathological findings in an HIV-positive patient with vacuolar myelopathy. On MRI symmetrical nonenhancing high-signal areas in the posterior columns on T2-weighted images result from extensive vacuolation visible on histological sections.

[Inflammatory facial paralysis in MRI. An overview]. / Die entzündliche Fazialisparese in der MRT. Eine Ubersichtsarbeit.

In inflammatory peripheral facial nerve palsy pathologically intense, linear and smooth enhancement of the distal intrameatal nerve segment can always be observed on T1-w- SE- MR sequences. The other nerve segments often present with a pathological enhancement as well. On T2-w- SE sequences, a thickening of the distal intrameatal nerve segment can be observed. The pathological enhancement persists over weeks and months; even in patients with complete clinical recovery, a persistent enhancement of the distal intrameatal nerve segment can be demonstrated. No correlation can be established between the intensity of the enhancement, the clinical condition and the electrophysiological data on electroneurography. The persistent enhancement of the different nerve segments is due to a long-lasting breakdown of the blood-peripheral nerve-barrier related to the process of degeneration and regeneration of the facial nerve in inflammatory palsy.

[Inflammatory diseases of the spinal cord and spinal nerve roots in the MRI]. / Entzündliche Erkrankungen des Rückenmarks und der Nervenwurzeln in der MRT.

PURPOSE: To evaluate characteristic and reliable MRI patterns of different inflammatory lesions of the spinal cord and the nerve roots in immunologically compromised and immunologically competent patients in order to be able to establish a correct diagnosis based on MRI findings. MATERIAL AND METHODS: The MRI examinations of 52 patients (27 men, 25 women, mean age 38.5 years, range 14-75 years) with proven inflammatory lesions (39 patients) or tumorous/postactinic lesions of the spinal cord (6 patients) and vascular malformations of the spinal cord (7 patients) were retrospectively analyzed. All examinations were performed on a 1.5 T MR unit, using bi- or triplanar T1-w pre- and postcontrast as well as T2-w SE sequences. Additionally, a review of the common medical literature concerning inflammatory lesions of the spinal cord was included. RESULTS: Clinical and radiological examinations allow a subdivision of inflammations of the spinal cord and the nerve roots into (meningoradiculo) myelitis and meningoradiculo (myelitis) in immunologically suppressed or competent patients. The MRI patterns of these two inflammatory subtypes vary: meningoradiculitis presents with an enhancement of the nerve roots and the leptomeninges; myelitis itself is characterized by single or multiple, diffuse or multifocal, with or without nodular, patchy or diffusely enhancing intramedullary lesions, with or without thickening of the cord and leptomeningeal inflammation. This differentiation helps to determine the underlying etiology in some of the patients. The immunologically suppressed patient suffers from viral infections (especially herpes simplex, varicella-zoster virus, cytomegalovirus), bacterinal infections (tuberculosis), but rarely from parasitic infections. The immunologically competent patient suffers from bacterial (borreliosis), but rarely viral infections, sarcoidosis and demyelinating diseases. Idiopathic myelitis is also common. CONCLUSIONS: Secondary ischemic and demyelinating processes result in a complex morphology of inflammatory lesions on MRI, and therefore the whole spectrum of demyelinating, ischemic and inflammatory lesions has to be included in the differential diagnosis. Even tumors may imitate inflammatory myelitis and radiculitis. Most commonly, meningoradiculitis can be separated from myelitis. A reliable diagnosis of a specific inflammatory lesion is difficult and is mostly achieved in patients with multiple sclerosis and in patients with HIV-associated cytomegalovirus infection.

Intensity of MR contrast enhancement does not correspond to clinical and electroneurographic findings in acute inflammatory facial nerve palsy.

PURPOSE: To determine the value of MR contrast enhancement in predicting the course of acute inflammatory facial nerve palsy and in selecting patients for surgical decompression. METHODS: Six patients with an acute inflammatory incomplete or complete peripheral facial nerve palsy (five idiopathic and one herpetic in origin) had repeated MR imaging studies with and without contrast enhancement, electroneurography, and clinical examinations to establish a connection between the intensity of contrast enhancement on MR images, the clinical condition, and the electrophysiological data. The examinations were performed every second day starting on the first day of admission until clinical recovery was proved by clinical deblockage (spontaneous clinical improvement). The last examination was performed 3 months after the onset of the facial nerve palsy. RESULTS: An abnormal, very intense contrast enhancement of the facial nerve was always present in the distal intrameatal and proximal tympanic segments and in the geniculate ganglion. The labyrinthine segment exhibited a mild to moderate enhancement, and the distal tympanic and mastoid segments showed a moderate to intense enhancement. The intensity of contrast enhancement did not correspond to the severity, duration, or course of the facial nerve palsy, and the electroneurographic data had no predictive value in indicating the severity of the inflammatory process. Three months after clinical recovery, a persistent and more or less unchanged or even slightly more intense contrast enhancement was observed. CONCLUSION: The long-lasting intense contrast enhancement seen in the facial nerve segments of patients who have acute peripheral inflammatory facial nerve palsy is explained by a two-phase breakdown of the blood-nerve barrier.

Cerebellomedullary compression in recessive craniometaphyseal dysplasia.

Craniometaphyseal dysplasia (CMD) is a very rare disorder of bone remodelling characterised by sclerosis of the skull base, vault and facial bones and metaphyseal splaying of tubular bones. The recessive form appears to be more severe than the dominant. Cranial nerve deficits have been reported in infancy and early childhood in a few patients, but the long-term history of recessive CMD is not well documented. We report cerebellomedullary compression in a girl with recessive CMD recognised at 14 years because of progressive truncal ataxia. MRI revealed backward angulation of the thickened clivus, narrowing of the foramen magnum and upward deviation of the cerebellum by a markedly thickened occipital squama, tonsillar herniation and obliteration of the infratentorial cerebrospinal fluid spaces. Posterior cranial fossa decompression resulted in marked improvement of the ataxia. Compression of posterior cranial fossa structures has to be considered in the natural history and management of CMD.

Tuberculoma mimicking meningioma of the falx cerebri. PCR diagnosis of mycobacterial DNA from formalin-fixed tissue.

We describe a 47-year-old patient with intracerebral tuberculoma of the falx cerebri and fronto-parietal cerebral cortex. The patient presented after a single episode of epileptic seizures. Computed tomography and MRI scans were suggestive of meningioma. At surgery a granulomatous tumor was removed that adhered to the cerebral cortex. The diagnosis of tuberculoma was verified by histology and growth in culture of mycobacterium tuberculosis. The patient recovered after surgery and chemotherapy. Three years later we confirmed the diagnosis using polymerase chain reaction for mycobacterial DNA sequences on the formalin-fixed, paraffin-embedded tissue.

Electrophysiology in the locked-in-syndrome.

We investigated five patients with a locked-in-syndrome (LIS) and reported the clinical, electrophysiologic, neuroradiologic, and neuropathologic findings. EEG reactivity was present in two and absent in three cases. Somatosensory evoked potentials (SEP) varied from unilaterally normal to bilaterally absent. We conclude that there is no specific pattern of SEP abnormality characteristic of LIS and that EEG reactivity cannot be taken as a sole measure of consciousness.