Uncovering a Role for the Dorsal Hippocampal Commissure in Recognition Memory

The dorsal hippocampal commissure (DHC) is a white matter tract that provides interhemispheric connections between temporal lobe brain regions. Despite the importance of these regions for learning and memory, there is scant evidence of a role for the DHC in successful memory performance. We used diffusion-weighted magnetic resonance imaging (DW-MRI) and white matter tractography to reconstruct the DHC in both humans (in vivo) and nonhuman primates (ex vivo). Across species, our findings demonstrate a close consistency between the known anatomy and tract reconstructions of the DHC. Anterograde tract-tracer techniques also highlighted the parahippocampal origins of DHC fibers in nonhuman primates. Finally, we derived diffusion tensor MRI metrics from the DHC in a large sample of human subjects to investigate whether interindividual variation in DHC microstructure is predictive of memory performance. The mean diffusivity of the DHC correlated with performance in a standardized recognition memory task, an effect that was not reproduced in a comparison commissure tract—the anterior commissure. These findings highlight a potential role for the DHC in recognition memory, and our tract reconstruction approach has the potential to generate further novel insights into the role of this previously understudied white matter tract in both health and disease.

Transverse sinus stenting for pseudotumor cerebri: a cost comparison with CSF shunting

BACKGROUND AND PURPOSE

Transverse sinus venous stent placement has been shown to lower intracranial pressure in patients with venogenic pseudotumor cerebri and to reverse, or at least stabilize, its symptoms and signs. There have been no studies comparing the cost of venous stenting with the time-honored treatment for pseudotumor cerebri-CSF shunting. The purpose of this study was to compare the cost of trasverse sinus stenting versus CSF shunting for the treatment of pseudotumor cerebri.

MATERIALS AND METHODS

This work was a retrospective cost analysis of individual resource use in 86 adults who were stented for pseudotumor cerebri during a 12-year period compared with resource use in 110 children who were shunted for hydrocephalus during a 3-year period.

RESULTS

There was no significant difference between the cost of inserting an initial venous stent ($13,863 ± 4890) versus inserting an initial CSF shunt ($15,797 ± 5442) (P = .6337) or between inserting an additional venous stent ($9421 ± 69) versus revising a CSF shunt ($10,470 ± 1245) (P = .4996). There were far fewer additional venous stent insertions per patient than there were subsequent CSF shunt revisions; 87% of stents placed required just 1 stent procedure, whereas only 45% of shunts required 1 shunt procedure. The main cause of the cost difference was the need for repeated revisions of the shunts, especially when they became infected-24 instances of a total 143 shunt procedures (16.8%) at an average cost of $84,729, approximately 5 times the cost of an initial shunt insertion.

CONCLUSIONS

Venous stenting costs significantly less per 100 procedures than does CSF shunting, due largely to the high cost of treating shunt infections and the need for repeated shunt revisions.

A pitfall in the reconstruction of fibre ODFs using spherical deconvolution of diffusion MRI data

Diffusion weighted (DW) MRI facilitates non-invasive quantification of tissue microstructure and, in combination with appropriate signal processing, three-dimensional estimates of fibrous orientation. In recent years, attention has shifted from the diffusion tensor model, which assumes a unimodal Gaussian diffusion displacement profile to recover fibre orientation (with various well-documented limitations), towards more complex high angular resolution diffusion imaging (HARDI) analysis techniques.

Spherical deconvolution (SD) approaches assume that the fibre orientation density function (fODF) within a voxel can be obtained by deconvolving a ‘common’ single fibre response function from the observed set of DW signals. In practice, this common response function is not known a priori and thus an estimated fibre response must be used. Here the establishment of this single-fibre response function is referred to as ‘calibration’. This work examines the vulnerability of two different SD approaches to inappropriate response function calibration: (1) constrained spherical harmonic deconvolution (CSHD)—a technique that exploits spherical harmonic basis sets and (2) damped Richardson–Lucy (dRL) deconvolution—a technique based on the standard Richardson–Lucy deconvolution.

Through simulations, the impact of a discrepancy between the calibrated diffusion profiles and the observed (‘Target’) DW-signals in both single and crossing-fibre configurations was investigated. The results show that CSHD produces spurious fODF peaks (consistent with well known ringing artefacts) as the discrepancy between calibration and target response increases, while dRL demonstrates a lower over-all sensitivity to miscalibration (with a calibration response function for a highly anisotropic fibre being optimal). However, dRL demonstrates a reduced ability to resolve low anisotropy crossing-fibres compared to CSHD. It is concluded that the range and spatial-distribution of expected single-fibre anisotropies within an image must be carefully considered to ensure selection of the appropriate algorithm, parameters and calibration. Failure to choose the calibration response function carefully may severely impact the quality of any resultant tractography.

Transverse sinus stenting for idiopathic intracranial hypertension: a review of 52 patients and of model predictions

BACKGROUND AND PURPOSE

Transverse sinus stenosis is common in patients with IIH. While the role of transverse sinus stenosis in IIH pathogenesis remains controversial, modeling studies suggest that stent placement within a transverse sinus stenosis with a significant pressure gradient should decrease cerebral venous pressure, improve CSF resorption in the venous system, and thereby reduce intracranial (CSF) pressure, improving the symptoms of IIH and reducing papilledema. We aimed to determine if IIH could be reliably treated by stent placement in transverse sinus stenosis.

MATERIALS AND METHODS

We reviewed the clinical, venographic, and intracranial pressure data before and after stent placement in transverse sinus stenosis in 52 of our own patients with IIH unresponsive to maximum acceptable medical treatment, treated since 2001 and followed between 2 months and 9 years.

RESULTS

Before stent placement, the mean superior sagittal sinus pressure was 34 mm Hg (462 mm H(2)0) with a mean transverse sinus stenosis gradient of 20 mm Hg. The mean lumbar CSF pressure before stent placement was 322 mm H(2)O. In all 52 patients, stent placement immediately eliminated the TSS pressure gradient, rapidly improved IIH symptoms, and abolished papilledema. In 6 patients, symptom relapse (headache) was associated with increased venous pressure and recurrent stenosis adjacent to the previous stent. In these cases, placement of another stent again removed the transverse sinus stenosis pressure gradient and improved symptoms. Of the 52 patients, 49 have been cured of all IIH symptoms.

CONCLUSIONS

These findings indicate a role for transverse sinus stent placement in the management of selected patients with IIH.

Influence of bone invasion and extent of mandibular resection on local control of cancers of the oral cavity and oropharynx

The aim of this paper was to evaluate the influence of bone invasion on treatment outcome among patients with cancers of the oral cavity and oropharynx and to determine whether or not outcome was influenced by the extent of mandibular resection. A review of 127 prospectively documented patients who were treated with marginal or segmental resection for oral (n = 110) and oropharyngeal (n = 17) cancers was undertaken. There were 97 males and 30 females with a median age of 61 years. Clinical T stages were: T1 17 patients, T2 33, T3 22, T4 55. Median followup was 4 years. A total of 94 patients underwent marginal resections and 33 underwent segmental resections. Histological bone invasion was present in 17 patients (16%) in the marginal resection group and 21 patients (64%) in the segmental group (P<0.05). Soft tissue surgical margins were positive in 11 patients (12%) in the marginal group and in seven patients (21%) in the segmental group (P=not significant). Local control did not correlate significantly with T stage, the extent of mandibular resection or the presence of histological bone invasion, but was significantly influenced by positive soft tissue margins (P<0.01). Among patients with bone invasion, the local control rate was higher following segmental resection when compared to marginal resections (87% vs 75%) but this was not statistically significant. Survival was significantly influenced by positive soft tissue margins but not bone invasion or the type of resection. We conclude that bone invasion alone did not predict for local control or survival rates among patients with oral and oropharyngeal cancers. Involved soft tissue margins were highly predictive of local recurrence and decreased survival. Conservative resection of the mandible is safe as long as marginal mandibulectomy does not lead to compromise of soft tissue margins. Segmental resection should be reserved for patients extensive bone invasion or those with limited invasion in a thin atrophic mandible.

Vestibular abnormalities in charge association

We report the vestibular abnormalities in 5 patients with the CHARGE association (Coloboma, Heart disease, Atresia of choanae, Retarded growth and development and/or central nervous system anomalies, Genital hypoplasia, and Ear anomalies). All patients had absent vestibular function as indicated by absent vestibulo-ocular reflexes and severe imbalance on simultaneous deprivation of proprioception and vision, as well as delayed motor development. All 6 semicircular canals were aplastic in each of the patients. While cochlear function was severely reduced in 6 of the 10 ears, it was absent only in 3 ears and was actually intact below 3 kHz in 1 ear. All 10 bony cochleas were present on computed tomography, and although 7 appeared abnormal, 3 appeared normal. This study confirms that absence of the bony semicircular canals in the presence of a bony cochlea is a characteristic finding in CHARGE association. It also demonstrates that these disproportionate structural abnormalities are reflected in the functional abnormalities: absent vestibular function with preservation of some cochlear function.

Disturbance of central vision after carbon monoxide poisoning

BACKGROUND

Cerebral achromatopsia is a disturbance of colour perception which may be complete or partial.

CLINICAL RECORD

A 28-year-old male patient presented five months after carbon monoxide poisoning with achromatopsia. The achromatopsia was unaccompanied by an inability to recognise faces (prosopagnosia) nor was there any disorder of form or depth perception.

RESULTS

Magnetic resonance imaging showed bilateral sharply defied areas of haemorrhagic infarction in the globus pallidus with extensive infarction involving temporal and occipital lobes and with apparent partial sparing of the visual cortex, presumably due to arterial insufficiency. The disturbance of central colour vision resolved spontaneously after a further period of 6 months.

CONCLUSION

The symptom of achromatopsia is analysed with particular reference to the recent work of Professor Zeki on disturbance of central colour vision following CO poisoning and the unusual MRI findings.

MR and positron emission tomography with fludeoxyglucose F 18 in gliomatosis cerebri

A 16-year-old girl presented with a unilateral third nerve palsy and predominant gray matter involvement on MR and positron emission tomography with fludeoxyglucose F 18. These findings were manifestations of gliomatosis cerebri. The antemortem diagnosis was made by partial temporal lobectomy.

Vertebral artery dissection diagnosed with CT

Vertebral artery dissection after neck manipulation has been well described. A case of bilateral vertebral artery dissection diagnosed with dynamic CT scanning of the neck is reported. The CT appearances and correlative angiographic and MR findings are presented.

Deflation of detachable balloons in the cavernous sinus by percutaneous puncture

The authors show that percutaneous puncture of balloons within the cavernous sinus is technically feasible and allows further access to the cavernous sinus after balloon detachment. Complete closure of a large carotid cavernous fistula was achieved in the 37-year-old trauma victim they treated using this technique.

Investigation of the blood pressure levels of workers occupationally exposed to salt

Publicity surrounding the salt and hypertension debate evoked fear in workers at a Salt Mine that their working conditions may lead to high blood pressure. A cross-sectional study was carried out to investigate the blood pressure levels of these workers. The blood pressure levels were found not to be raised in comparison with those of a similar group of workers not occupationally exposed to salt.

Radiologic evaluation of the normal and diseased posterior cervical space

The posterior cervical space seen on cross-sectional imaging of the neck constitutes most of the posterior triangle seen on clinical examination. Although triangular anatomy relates best to the surface perspective of the clinician, a spatial approach to anatomy works better for the radiologist viewing axial images. The posterior cervical space is defined as the area in the posterolateral portion of the neck from the skull base to the clavicles deep to the sternomastoid and trapezius muscles but superficial to the prevertebral space. Its principal contents are fat, the spinal accessory nerve, and lymph nodes. We analyzed CT and MR images and clinical records of 63 patients known or suspected to have disease of the posterior cervical space to determine the imaging features that mark a lesion as originating in the posterior cervical space and the spectrum of diseases that arise there. Of the 63 patients in the study, four had clinical pseudomasses, nine had congenital lesions, 10 had inflammatory disease, six had benign tumors, and 34 had malignant tumors. A typical mass lesion of the posterior cervical space was centered within the fat of the space, between the deep and superficial layers of the deep cervical fascia. Characteristic displacements caused by a mass in the posterior cervical space included anteromedial displacement of the carotid space and posteromedial displacement of the prevertebral space. Our study shows that the differential diagnosis of lesions of the posterior cervical space reflects the normal contents of the space, and that diagnosis can thereby be predicted from knowledge of the normal anatomy and contents of the space.

Mortality of employees in plants manufacturing 4,4'-bipyridyl

A historical-prospective cohort study was conducted of 729 male employees of plants manufacturing 4,4'-bipyridyl. The cohort was studied because employment in some of the plants had been linked to malignant and nonmalignant skin lesions attributed to exposure to tarry by-products. The overall mortality experience of the cohort did not show any statistically significant findings. More-detailed analysis of subdivision of the cohort gave results that justified further inquiry into lung cancer incidence. A nested case-referent study did not indicate that any occupational factor other than employment in a bipyridyl plant was related to the incidence of lung cancer. The epidemiologic, toxicologic, and industrial hygiene information was assessed, and it was concluded that there was no evidence of a plausible occupational hazard of lung cancer to the bipyridyl workers, but that a follow-up of the cohort after an interval of five years should be undertaken.

Clinical-radiologic issues in perineural tumor spread of malignant diseases of the extracranial head and neck

The radiologic and clinical records of 52 patients with radiologically documented perineural tumor were reviewed to assess the spectrum of tumors responsible, the nerves most commonly involved, and the optimal methods for imaging perineural tumor infiltration. Perineural tumor infiltration was most commonly seen with head and neck squamous cell carcinoma, followed by adenoid cystic carcinoma and several others, such as non-Hodgkin lymphoma, malignant schwannoma, minor salivary gland malignancy, and other sarcomas. The second and third divisions of the trigeminal nerve and the facial nerve were most commonly involved with perineural tumor. Both antegrade and retrograde perineural tumor spread were seen, although retrograde spread was significantly more common. Both high-resolution direct coronal computed tomography and magnetic resonance (MR) imaging clearly showed perineural tumor below the skull base. MR imaging best depicted skull base, cisternal, and brain stem perineural tumor infiltration. T1-weighted MR imaging before and after administration of gadopentetate dimeglumine is the study of choice in investigation of perineural tumor.

CT and MR imaging of fourth ventricular meningiomas

True fourth ventricular meningiomas are rare. We report two cases, one with typical CT, angiographic, and magnetic resonance (MR) appearances and one with atypical features of central cyst formation on CT and MR. The utility of MR in demonstrating intraventricular location in three imaging planes is illustrated. Given the rarity of these tumors, atypical features may preclude accurate preoperative diagnosis, even with MR.

Cervical myelopathy in C.P.P.D. deposition disease

Cervical Myelopathy is a rare manifestation of calcium pyrophosphate dihydrate (C.P.P.D.) deposition disease. A case is presented where radiographically noncalcified extradural masses containing C.P.P.D. crystals were present at the C7 level, producing cord compression and neurological symptoms. These masses are thought to represent para-articular deposits related to the adjacent facet joints.

Massive intramural duodenal haematoma following blunt abdominal trauma. Case report

We report a case of a massive intramural duodenal haematoma following blunt abdominal trauma. The value of computed tomography and other imaging modalities is discussed.

Galileo, Planetary Atmospheres, and Prograde Revolution

Early in March 1610 Galileo was preoccupied with curious brightness variations of the newly discovered satellites of Jupiter. In formulating an incorrect explanation he advanced important generalizations about the existence of planetary atmospheres and counterclockwise circulation within the solar system.