Thyroid dysfunction and exudative age-related macular degeneration - A longitudinal nationwide registry-based cohort study

PURPOSE

The association between thyroid dysfunction and exudative age-related macular degeneration (AMD) is unknown.

METHODS

In this Danish longitudinal nationwide registry-based cohort study we included all Danish residents aged 50-100 between 2008 and 2018. Using the Danish national registries, we studied the association between thyroid dysfunction and exudative AMD. Thyroid dysfunction was classified as two consecutive redeemed prescriptions of thyroid hormones (hypothyroidism) or anti-thyroid medication (hyperthyroidism). Exudative AMD was classified as an ICD diagnosis of AMD and a code for anti-VEGF treatment. All patients are treated for exudative AMD in a hospital in Denmark, and we therefore have complete registration of this patient group.

RESULTS

We included 2 087 305 individuals, of which 1 072 567 (51.4%) were women; 59 318 (2.8%) had hypothyroidism, and 33 922 (1.6%) had hyperthyroidism. During a median follow-up of 11 years, 26 998 (1.3%) people developed exudative AMD. Hypothyroidism (adjusted hazard ratio [HR]: 1.17; 95% confidence interval [CI] 1.10-1.25; p < 0.001) and hyperthyroidism (HR: 1.23; 95% CI:1.13-1.34; p < 0.001) were both associated with the development of exudative AMD. The age-stratified analyses yielded similar results to the main analyses, except that the risks were exaggerated in the older part of the population.

CONCLUSION

This is the first longitudinal nationwide study showing that both hypo- and hyperthyroidism are associated with an increased risk of exudative AMD. AMD is a quantitative problem in the population and our findings could have a public health impact. Further studies are needed to study the underlying mechanisms of the association.

Topical anaesthesia in strabismus surgery for Graves' orbitopathy: a comparative study of 111 patients

PURPOSE

To evaluate the tolerability and usability of topical anaesthesia in single rectus muscle recession for strabismus caused by Graves' orbitopathy (GO). To compare the perioperative pain score and surgical outcome between GO patients and non-GO patients.

METHODS

A retrospective comparative study of consecutive single rectus muscle recession performed under topical anaesthesia was carried out. All patients scheduled for one-stage single rectus muscle recession under topical anaesthesia were included. Numerical visual analogue pain score scale (NVAS) points, rates of motor success (horizontal deviation < 8 prism diopters (PD) and vertical deviation ≤ 6 PD) and sensory success (no diplopia without prisms), complications and postoperative adjustment frequencies were compared between GO and non-GO patients.

RESULTS

A total of 111 patients were included. The mean perioperative pain scores were 2.3 (SD ± 1.3) in GO and 1.6 (SD ± 1.1) in non-GO patients (p = 0.06 adjusted for gender). The postoperative mean alignments in GO and non-GO patients were 2 versus 3 PD horizontally and 1 versus 1 PD vertically respectively. Both motor and sensory success rates were 98% in GO patients and 94% versus 93% in non-GO patients. Adjustments as a second procedure the day after surgery was performed in 10% of the GO patients and 15% of the non-GO patients. The oculocardiac reflex was not triggered in any of the GO patients.

CONCLUSION

Topical anaesthesia in single muscle recession for GO is safe, well-tolerated and gives comparable surgical outcomes to those achieved in non-GO patients.

Nationwide Incidence of Thyroid Eye Disease and Cumulative Incidence of Strabismus and Surgical Interventions in Denmark

Importance

Thyroid eye disease (TED) is a serious condition that can cause proptosis and strabismus and, in rare cases, lead to blindness. Incidence data for TED and strabismus and surgical interventions after TED are sparce.

Objective

To investigate the nationwide incidence of TED, strabismus, and surgical interventions associated with TED.

Design, Setting, and Participants

A Danish nationwide registry-based cohort study between 2000, which marks the beginning of uniform coding for the decompression surgery nationwide, and 2018. The cohort consisted of a mean 4.3 million people aged 18 to 100 years with no prior TED diagnosis each year. Total observation time was 8.22 × 107 person-years (women, 4.18 × 107 person-years; men, 4.04 × 107 person-years).

Main Outcome Measures

The annual numeric and age-standardized incidence of hospital-treated TED and cumulative incidence of strabismus, strabismus surgery, and orbital decompression surgery in patients with TED. The incidence was stratified by sex, thyroid diagnosis, and age.

Results

A total of 4106 incident diagnoses of TED were identified during 19 years among 3344 women (81.4%) and 762 men (18.6%). The mean numeric annual nationwide incidence rate of TED was 5.0 per 100 000 person-years overall, 8.0 per 100 000 person-years in women, and 1.9 per 100 000 person-years in men, resulting in a 4:1 ratio of women to men with TED. The age-standardized incidence was similar. The mean (SD) age at onset was 51.3 (14.5) years. At the time of TED diagnosis, 611 patients (14.9%) were euthyroid, 477 (11.6%) were hypothyroid, and 3018 (73.5%) were hyperthyroid. In patients with TED who were euthyroid, the 4-year cumulative incidence was 41% for antithyroid medication and 13% for L-thyroxine. In patients with TED, the 4-year cumulative incidence for strabismus was 10%. The 4-year cumulative incidence of surgical interventions after TED was 8% for strabismus surgery and 5% for orbital decompression. At 4 years, strabismus surgery was more common in men (13.3%; 95% CI, 10.75-15.86) than in women (7.2%; 95% CI, 6.24-8.08), and the absolute difference was 6.1% (95% CI, 3.42-8.14; P < .001).

Conclusions and Relevance

This study in Denmark provides nationwide empirical incidence of TED and strabismus and surgical interventions after TED that required inpatient or outpatient hospital treatment, and might be used for patient information and health care planning.

Epidemiology and clinical characteristics of congenital choristomas in the ocular adnexa of pediatric patients

PURPOSE

To investigate the epidemiology and clinical characteristics of infants presenting with conjunctival, palpebral, or orbital congenital choristomas (dermolipomas, epidermoids, and dermoid cysts) and children undergoing surgery for congenital choristomas in the ocular adnexa.

METHODS

We reviewed the medical files of congenital choristomas in children seen in The Capital Region of Denmark during a 5-year period (2014-2018). Children (< 18 years) were divided into two groups: those referred < 1 year of age (Group I) and those undergoing surgery to remove the lesion (Group II). Group I was used to calculate a population-based incidence of congenital choristomas by comparing our data to birth statistics from the Danish Medical Birth Registry.

RESULTS

A total of 97 children were included, 43 in Group I and 70 in Group II (including 16 patients from Group I). The total incidence of congenital choristomas was 1 in 2537 live born children. Most lesions were palpebral choristomas (27/43, 63%) located in the superotemporal region (17/27, 63%), followed by the superonasal region (7/27, 26%). The main reasons for surgical removal of a congenital choristoma were growth (28/70, 40%) or cosmesis (25/70, 36%).

CONCLUSION

The total incidence of congenital choristomas in the ocular adnexa of infants < 1 year of age, including both conjunctival and palpebral congenital choristomas, is about 1 in 2537 live born children in The Capital Region of Denmark. Hence, congenital choristomas are common masses found in the ocular adnexa.

Genomic Alterations in Human Papillomavirus-Positive and -Negative Conjunctival Squamous Cell Carcinomas

Purpose

The genomic alterations contributing to the pathogenesis of conjunctival squamous cell carcinomas (SCCs) and their precursor lesions are poorly understood and hamper our ability to develop molecular therapies to reduce the recurrence rates and treatment-related morbidities of this disease. We aimed to characterize the somatic DNA alterations in human papillomavirus (HPV)-positive and HPV-negative conjunctival SCC.

Methods

Patients diagnosed with conjunctival SCC in situ or SCC treated in ocular oncology referral centers in Denmark were included. HPV detection (HPV DNA PCR, p16 immunohistochemistry, and mRNA in situ hybridization) and targeted capture-based next-generation sequencing of 523 genes frequently involved in cancer were performed to describe the mutational profile based on HPV status.

Results

Tumor tissue was available in 33 cases (n = 8 conjunctival SCCs in situ, n = 25 conjunctival SCCs), constituting 25 male and 8 female patients. Nine cases were HPV positive. The HPV-positive SCCs in situ and SCCs were characterized by transcriptionally active high-risk HPV (types 16 and 39) within the tumor cells, frequent mutations in PIK3CA (n = 5/9), and wild-type TP53, CDKN2A, and RB1, while the HPV-negative counterparts harbored frequent mutations in TP53 (n = 21/24), CDKN2A (n = 7/24), and RB1 (n = 6/24).

Conclusions

Our findings have delineated two potentially distinct distributions of somatic mutations in conjunctival SCC based on HPV status-pointing to different biological mechanisms of carcinogenesis. The present findings support a causal role of HPV in a subset of conjunctival SCC.

Human papillomavirus infection plays a role in conjunctival squamous cell carcinoma: a systematic review and meta-analysis of observational studies

PURPOSE

We aimed to study the prevalence of human papillomavirus (HPV) in conjunctival intraepithelial neoplasia and carcinoma. Furthermore, we aimed to explore whether geographical differences or different detection modalities are associated with the conflicting information regarding HPV and the development of the disease.

METHODS

We searched the MEDLINE, EMBASE and Scopus databases for studies reporting on HPV and conjunctival intraepithelial neoplasia or carcinoma. The pooled prevalence proportions, odds ratio (OR) and corresponding 95% confidence intervals were calculated assuming a random-effects model. Subgroup analyses and meta-regression explored possible sources of heterogeneity.

RESULTS

A total of 39 studies were included in the systematic review. The pooled prevalence of HPV in conjunctival intraepithelial neoplasia and carcinoma was 26%, with HPV16, 18, and 33 being the most frequently reported genotypes. Human papillomavirus (HPV) infection was associated with an increased risk of conjunctival intraepithelial neoplasia and carcinoma (OR 8.4, 95% confidence interval (CI) 3.7-19.1); lower in studies from African countries (OR 1.7, 95% CI 0.9-3.5) than other countries (OR 16.1, 95% CI 5.8-44.3), p = 0.013.

CONCLUSION

Human papillomavirus infection increases the odds of conjunctival intraepithelial neoplasia and carcinoma by 8.4 compared to healthy conjunctival mucosa or other ocular surface diseases. There seem to be geographical differences regarding HPV in conjunctival intraepithelial neoplasia and carcinoma. HPV16 was the most prevalent genotype, followed by HPV18 and HPV33, meaning that most of the HPV-related conjunctival intraepithelial neoplasia and carcinoma may be prevented by the HPV vaccines that are currently available.

Unilateral Optic Nerve Sheath Fenestration in Idiopathic Intracranial Hypertension: A 6-Month Follow-Up Study on Visual Outcome and Prognostic Markers

Loss of vision is a feared consequence of idiopathic intracranial hypertension (IIH). Optic nerve sheath fenestration (ONSF) may be an effective surgical approach to protect visual function in medically refractory IIH. In this study, we evaluate the impact of unilateral superomedial transconjunctival ONSF on bilateral visual outcome using a comprehensive follow-up program. A retrospective chart review of IIH patients who underwent unilateral ONSF between January 2016 and March 2021 was conducted. Patients fulfilling the revised Friedman criteria for IIH and who had exclusively received ONSF as a surgical treatment were included. Main outcomes were visual acuity (VA); perimetric mean deviation (PMD); papilledema grade; and optic nerve head elevation (maxONHE) 1 week, 2 weeks, and 1, 3, and 6 months after surgery. VA (p < 0.05), PMD (p < 0.05), papilledema grade (p < 0.01), and maxOHNE (p < 0.001) were improved after 6 months on both the operated and non-operated eye. Prolonged surgical delay impedes PMD improvement (r = -0.78, p < 0.01), and an increasing opening pressure initiates a greater ganglion cell loss (r = -0.79, p < 0.01). In this small case series, we demonstrate that unilateral superonasal transconjunctival ONSF is a safe procedure with an effect on both eyes. Optic nerve head elevation and PMD are feasible biomarkers for assessing early treatment efficacy after ONSF.

Primary Orbital Chondromyxoid Fibroma: A Cause of Monosymptomatic Periocular Pain

Chondromyxoid fibroma (CMF) is a very rare entity, accounting for <1% of all bone tumours. So far, only 4 cases have been reported with the orbit as primary location. Here, we present a case of orbital CMF with periocular pain as the presenting symptom and as the only symptom when the tumour recurred after surgery. A 41-year-old man underwent a CT scan and later an MRI as part of evaluation for left periocular pain that had persisted for a year. Clinical examination was normal. CT and MRI revealed an irregular mass in the lateral part of the left orbital roof. The tumour was removed by curettage, and histopathological examination showed a CMF. The pain was absent for 3 months. A second MRI 5 months postoperatively revealed a recurrence, which was removed surgically, resulting in pain alleviation. In conclusion, CMF is a potential cause of periocular pain, and persistent periocular pain with normal clinical findings should warrant a CT or MRI scan.

Safety and feasibility of mesenchymal stem cell therapy in patients with aqueous deficient dry eye disease

PURPOSE

To evaluate the safety and feasibility of injecting allogeneic adipose-derived mesenchymal stem cells (ASCs) into the lacrimal gland (LG) as a treatment of aqueous deficient dry eye disease (ADDE).

METHODS

In this open-label, 5-visit clinical trial (baseline, treatment and weeks 1, 4 and 16) seven subjects with ADDE received one transconjunctival injection of allogeneic ASCs into the LG in one eye. The ASC product contained 22 million ASCs/ml and the injected volume was maximally 50% of the LG volume as determined on magnetic resonance imaging (MRI). Treatment related adverse events (AEs) were assessed at each visit (primary endpoint). Ocular Surface Disease Index (OSDI), tear osmolarity, tear film breakup time (TBUT), corneal staining (Oxford grade) and Schirmer's I test were assessed at each timepoint.

RESULTS

No AEs related to the study treatment were observed. Mean follow-up time was 126 days after treatment. The mean OSDI score decreased from 58.9 ± 20.6 at baseline to 34.1 ± 21.6 (p < 0.002). In the study eye mean tear osmolarity decreased from 312.9 ± 10.4 to 291.6 ± 10.9 mosm/l (p < 0.002), mean TBUT increased from 3.7 ± 1.5 to 7.1 ± 1.9 s (p < 0.002), mean Schirmer's I test increased from 4.6 ± 0.7 to 8.1 ± 3.1 mm/5 min (p < 0.03), while mean Oxford grade showed a trend towards a decrease from 2.4 ± 0.7 to 1.3 ± 1 (p < 0.10).

CONCLUSION

Our trial suggests that injection of allogeneic ASCs into the LG is a safe and feasible treatment of severe ADDE. A randomized placebo-controlled trial aimed at elucidating the therapeutic effect of allogeneic ASCs in a larger patient cohort from our research group is currently underway.

Carcinomas of the lacrimal drainage system

Malignant tumors of epithelial origin are the most frequent neoplasms of the lacrimal drainage system (LDS). A total of 539 cases are reported in the literature from 1960 to 2019. LDS carcinoma is a disease of the middle-aged and elderly population, with a median age at diagnosis of 57 years. Overall, there is a slight male predominance. Reported risk factors are chronic inflammation, LDS papilloma, and infection with oncogenic viruses. Symptoms of an LDS carcinoma resemble those of benign, inflammatory diseases, with epiphora from obstruction of the LDS as the most frequently encountered symptom. The median time from symptoms to diagnosis is 12 months and even longer for patients reporting epiphora as the only initial symptom. This diagnostic delay leads to a substantial fraction of patients with locally advanced tumors and lymph node spread at the time of diagnosis. Surgery with adjuvant radiotherapy is the treatment of choice for most patients; however, the extension and aggressiveness of the disease and the patient's general health and preferences determine the definite treatment. Five-year overall survival is reported to range from 61 to 87.6%. A large tumor size and positive lymph node status correlate with a decreased overall and disease-free survival.

Development and validation of a multiple-choice questionnaire-based theoretical test in direct ophthalmoscopy

PURPOSE

Direct ophthalmoscopy can reveal systemic, neurologic and ophthalmic conditions, but is poorly mastered among young physicians. A theoretical test is needed to measure effect of educational interventions. We developed and gathered validity evidence for a multiple-choice questionnaire (MCQ)-based theoretical test in direct ophthalmoscopy.

METHODS

The MCQ was developed by interviewing experts. Then, validity evidence was evaluated using Messick's validity framework. Content was ensured by inviting the experts to contribute in a Delphi-like process. Response process was ensured by piloting and by streamlining all instructions. Then, the test was taken by ophthalmologists and by medical students without experience in direct ophthalmoscopy. Results were used to evaluate internal structure (item quality analysis and internal consistency), relations to other variables (correlation of test scores to experience level) and consequences (establishment of pass-fail score and the consequences of its use).

RESULTS

The first phase of the study yielded 100 MCQs. In second phase, we identified that 60 items fulfilled predefined relevance and item quality requirements. These items demonstrated very high internal consistency (Cronbach's alpha = 0.95), significantly discriminated medical students from specialists (p < 0.001, independent samples t-test) and the established pass-fail score of 50 (83%) correct answers resulted in no false positives (students passing) and no false negatives (specialists failing). A Decision study identified that sampling 15 items suffice for certification.

CONCLUSION

We developed and validated an MCQ-based theoretical test in direct ophthalmoscopy that enables an evidence-based approach to measuring, evaluating and certifying the theoretical knowledge necessary for direct ophthalmoscopy.

Conjunctival intraepithelial neoplasia and carcinoma: distinct clinical and histological features in relation to human papilloma virus status

AIMS

Human papillomavirus (HPV) is considered a causative agent for the development of a broad range of human carcinomas. The role of HPV in the development of conjunctival intraepithelial neoplasia (CIN) and carcinoma (cSCC) remains unclear. The purpose of the present study was to investigate the HPV prevalence in a nationwide cohort and to describe clinical and histopathological features in relation to HPV status.

METHODS

All cases of CIN and cSCC in Denmark from 1980 to 2016 were included. We combined p16 immunohistochemistry (IHC), RNA in situ hybridisation (RNA ISH) and HPV DNA PCR to detect HPV. The results were correlated to clinical and histopathological parameters.

RESULTS

One hundred twelve primary tumours and 33 recurrent tumours were included for HPV analysis. Twenty-four (21%) of the primary tumours were HPV positive by PCR. Eighteen of out 19 HPV-positive tumours were positive by RNA ISH. HPV16 was the most prevalent genotype (n=18, 75%). The patients with HPV-positive tumours were significantly younger (mean difference 11.5 years, 95% CI 5.2 to 17.9, p=0.0005) and had a higher recurrence compared with patients with HPV-negative tumours (HR 2.30, 95% CI 1.02 to 5.21, p=0.046). The HPV-positive tumours were associated with a positive p16 IHC and a non-keratinising morphology.

CONCLUSION

We describe distinct clinical and histopathological features associated with HPV status in cSCC. The finding of transcriptionally active HPV in this material lends support to a causal role of HPV in a subset of cSCC.

Genomic and immunohistochemical characterisation of a lacrimal gland oncocytoma and review of literature

The aim of the present study was to report the genetic and immunohistochemical profile of a rare case of lacrimal gland oncocytoma. A 20-year-old male underwent magnetic resonance imaging (MRI) due to viral encephalitis. Notably, the MRI revealed a multicystic tumor in the left lacrimal gland. A lateral orbitotomy was performed and the tumor was completely excised. Four months following surgery, the patient was free of symptoms. Histopathologically, the tumor was composed of large, eosinophilic and polyhedral cells with small round nuclei. The tumor cells stained strongly for antimitochondrial antibody MU213-UC, cytokeratin (CK) 5/6, CK 7, CK 17, CK 8/18 and CK 19. The final diagnosis was an oncocytoma of the lacrimal gland without any signs of malignancy. Array-based comparative genomic hybridisation demonstrated a gain of one copy of chromosome 8 and loss of one copy of chromosome 22 as the sole genomic imbalances. These chromosomal alterations have not previously been identified in oncocytoma and may be specific to lacrimal gland oncocytoma. Sequencing of the mitochondrial genome demonstrated multiple alterations of the NADH-ubiquinone oxidoreductase chain 5 (ND5) gene involved in mitochondrial oxidative phosphorylation. This may support the notion of a common genetic background of oncocytic lesions in the lacrimal gland and other anatomical sites.

Surgical Timing of the Orbital "Blowout" Fracture: A Systematic Review and Meta-analysis

OBJECTIVE

The orbital blowout fracture is a common facial injury, carrying with it a risk of visual impairment and undesirable cosmetic results unless treated properly. Optimal timing of the surgical treatment is still a matter of debate. We set out to determine whether a meta-analysis would bring us closer to an answer to this question.

DATA SOURCES

PubMed, EMBASE, Web of Science, and the Cochrane Library were searched from January 1980 to August 2014. We applied the following inclusion criteria: isolated blowout fractures, presenting early and late surgery groups (<14 and >14 days). Patients were evaluated for diplopia and enophthalmos.

REVIEW METHODS

We followed the statements of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses). Pooled odds ratios were estimated with the fixed effects method of Mantel-Haenszel.

RESULTS

We identified 5 studies with available outcome data (N = 442). Patients in the late group showed an odds ratio of 3.3 (P = .027) for persistent postoperative diplopia as compared with the early group. We found no significant difference between the groups when assessing postoperative enophthalmos as an isolated symptom.

CONCLUSION

We found a significantly increased risk of persistent diplopia in patients who were operated >14 days after the trauma.

The functional outcome of blow-out fractures managed surgically and conservatively: our experience in 100 patients

The proportion of orbital blow-out fractures (BOFs) which are operated upon varies. The purpose of this study was to determine the treatment pattern of BOFs at our tertiary trauma centre and to evaluate the functional outcomes in patients according to whether they were managed surgically or conservatively. The study design is a retrospective cohort study and the setting is Tertiary care University Hospital. The participants include patients with isolated BOFs admitted to our Trauma Unit from 2010 to 2013. Of the 100 consecutive patients included, 60 had available follow-up data. The presence of diplopia and enophthalmus was determined by reviewing the medical records. Data from the patients' initial consultation and their 3-month follow-up were also collected. Of the 60 patients whose data could be analysed, 36 had been managed surgically and 24 conservatively. Of the patients managed surgically, 25 had diplopia in peripheral gaze before surgery and 12 at 3-month follow-up. Nine had diplopia in primary gaze before surgery and none at 3-month follow-up. Five had enophthalmus before surgery and two at 3-month follow-up. Of the patients managed conservatively, eight had diplopia in peripheral gaze initially and seven at 3-month follow-up. Three had diplopia in primary gaze initially and one at 3-month follow-up. One had enophthalmus initially which was still present at 3-month follow-up. Primary gaze diplopia disappeared while secondary gaze diplopia was present in about a third of patients, whether managed surgically or conservatively at the 3-month follow-up. Standardised follow-up as well as clear indications for and against surgery are warranted.

Long term follow-up of persistent choroidal folds and hyperopic shift after complete removal of a retrobulbar mass

Background

Hyperopic shift and chorioretinal folds are common findings with intraorbital masses compressing the posterior pole of the globe. These signs usually regress after complete tumour excision. To the best of our knowledge this is the first reported case, where optical coherence tomography was used to document persistent chorioretinal folds after complete excision of a retrobulbar mass.

Case presentation

A 47-year-old Caucasian woman was referred to our department with long-documented hyperopic shift and gradually decreasing vision in her left eye. Optical coherence tomography showed chorioretinal folds. Magnetic resonance imaging revealed a retrobulbar mass which caused flattening of the posterior pole of the globe. The tumour was successfully removed, and was confirmed to be a cavernous haemangioma on histological assessment. 3 years after surgery the patient still has a similar amount of hyperopia and chorioretinal folds.

Conclusion

Choroidal folds and hyperopic shift may persist after complete tumour removal. Long term follow-up is advised to rule out recurrence of the intraorbital mass.

Squamous cell dysplasia and carcinoma of the conjunctiva. A nationwide, retrospective, epidemiological study of Danish patients

PURPOSE

To investigate the epidemiology of squamous cell dysplasia and carcinoma of the conjunctiva in Denmark.

METHODS

Review of the histopathological case reports at the Eye Pathology Institute (EPI), University of Copenhagen, and the National Danish Pathology Bank from 1980 to 2011. Information regarding distribution of age and sex, localization, earlier pathology, comorbidity and recurrence of the condition was registered. The Cause of Death Registry at Statens Serum Institut was used to obtain information regarding cause of death.

RESULTS

A total of 143 cases were identified. Ninety-five (61%) had epithelial dysplasia, 19 (13%) had carcinoma in situ, and 29 (20%) had squamous cell carcinoma. A significantly higher proportion of men were found. The median age at diagnosis was 65 years. The risk of recurrence was 10.0% [95% confidence interval (CI): 5.0-15.0] after 1 year and 17.2% (95% CI: 10.8-23.7) after 5 years. The lesions were most often localized to the corneal limbus. In our records, one patient had a lymph node metastasis and the disease necessitated enucleation in two patients. No patients had died from squamous cell carcinoma of the conjunctiva.

CONCLUSION

Overall, our data are in agreement with the results of previous studies in Northern, high-latitude countries. There is a low incidence rate; the lesions are predominantly seen in men in their seventh decade and localized to the corneal limbus. The risk of recurrence is high, and the benign lesions have potential to progress to frank carcinoma.

Expression of filaggrin in normal and keratinized conjunctiva

Purpose:

We wanted to investigate filaggrin expression in normal conjunctiva and in conjunctiva exposed to different degrees of mechanical stress. Mechanical stress results in parakeratinization of the conjunctiva. If filaggrin is expressed in the milder forms of parakeratinization, it might be used as a sensitive marker of mechanical stress.

Methods:

Immunohistochemical staining using antibodies to filaggrin was performed on paraffin sections of normal human conjunctiva, and on conjunctiva with different degrees of mechanical conjunctival stress.

Results:

Filaggrin was not expressed in the normal conjunctiva, nor in conjunctiva with milder forms of mechanical stress. Intense staining of filaggrin was seen in the conjunctiva of a patient with Stevens-Johnson syndrome, and marked expression of filaggrin was found in the conjunctival epithelium of a patient with moderate dysplasia of the conjunctiva.

Conclusion:

Filaggrin is not a sensitive marker of mechanical stress; it is, however, expressed in some moderate and severe forms of parakeratinization of the conjunctiva.

Treatment of orbital inflammation with rituximab in Wegener's granulomatosis

OBJECTIVES

To study the efficacy of rituximab therapy for the treatment of orbital inflammation in patients with Wegener's granulomatosis (WG).

METHODS

Ten WG patients with orbital inflammation were included in this case-series. None had symptoms suggestive of extra-orbital disease activity. Immunosuppressive medication (mycophenolate and prednisolone) was administered to 3 patients at the time of rituximab therapy. Three patients had previously been treated with anti-tumour-necrosis-factor-alpha antibodies, and one of these patients had also received cyclophosphamide as treatment for orbital inflammation. All patients were treated with 1000 mg of rituximab administered twice with an interval of 14 days between the infusions. Six months after therapy, a physical examination and a control computerised tomography (CT) scan was performed.

RESULTS

All patients had orbital inflammation demonstrated by CT-scan before treatment (3 had bilateral and 7 unilateral orbital involvement). Orbital symptoms at study baseline included pain, pressure sensation behind the eyes, epiphora, diplopia, and affection of the visual acuity. Nine out of ten patients experienced subjective improvement. Four patients (seven eyes) with visual impairment responded to therapy, and the improvement in visual acuity was sustained throughout follow-up (median duration of follow-up: 17 months; range: 6-18 months). At the time of the control CT-scan, size-reduction of the orbital mass was observed in two patients, while the size of the orbital mass was unchanged in eight patients.

CONCLUSIONS

Rituximab therapy has positive effects on symptoms, visual acuity and/or granuloma size in some WG patients with orbital inflammation. Treatment with rituximab should be considered in WG patients with this serious manifestation of the disease.

Malignant transformation of a medulloepithelioma of the optic nerve

OBJECTIVE

To describe a case of malignant transformation of a medulloepithelioma of the optic nerve.

METHODS

A 3-year-old boy presented with right-sided proptosis, swollen eyelids, restricted ocular movements, pain and nausea. Visual acuity was hand motions. A benign non-teratoid medulloepithelioma of the optic nerve was surgically removed. Due to relapse in the orbit 10 months postoperatively enucleation and partial orbital exenteration were performed. Light microscopy and immunohistochemistry now revealed a malignant medulloepithelioma. The boy was further treated with chemotherapy and radiotherapy and is still alive 36 months after primary surgery.

RESULTS

Medulloepithelioma of the optic nerve is extremely rare. Only eight cases have been described in the literature. Unlike intraocular medulloepithelioma, all have been malignant tumours. This is the first case described of a benign medulloepithelioma of the optic nerve, later transforming into a malignant tumour. One third of patients with medulloepithelioma of the optic nerve have died from direct intracranial spread or metastasis to the central nervous system (CNS).

CONCLUSIONS

Medulloepithelioma of the optic nerve should be considered malignant despite morphology with tendency to spread to the CNS. Furthermore; it should be considered as a differential diagnosis when observing a tumour of the optic nerve in a child.

Native iron in the continental lower crust: petrological and geophysical implications

Lower crustal granulite xenoliths recovered from a kimberlite pipe in western Africa contain native iron (Fe(0)) as a decomposition product of garnet and ilmenite. Magnetic measurements show that less than 0.1 percent (by volume) of iron metal is present. Data from geothermometry and oxygen geobarometry indicate that the oxide and metal phases equilibrated between iron-wüstite and magnetite-wüstite buffers, which may represent the oxidation state of the continental lower crust, and the depleted lithospheric upper mantle. Ferromagnetic native iron could be stable to a depth of approximately 95 kilometers and should be considered in the interpretation of long-wavelength static magnetic anomalies.

Review of 345 eye amputations carried out in the period 1996-2003, at Rigshospitalet, Denmark

PURPOSE

The aim of this study was to identify the number of eye amputations, and the causative diagnoses, indications for surgery and surgical techniques applied, and to evaluate a possible change in surgical technique in a tertiary referral centre in Denmark.

METHODS

The hospital database was screened using surgery codes for patients who had undergone bulbar evisceration, enucleation or orbital exenteration in the period 1996-2003. Patient records were reviewed for gender, age, time since surgery, causative diagnosis (the disease process leading to the indication for amputation), indication for eye amputation, type of surgery and whether an implant was applied.

RESULTS

A total of 345 patients were identified as having undergone eye amputation during the 8-year period. Indications for eye amputation were: painful blind eye (127); neoplasm (119); infection (42); recent injury (25); disfiguring blind eye (25); prevention of sympathetic ophthalmia (5), and other reasons (2). Surgical procedures included 174 eviscerations, 154 enucleations and 17 orbital exenterations. The mean number of surgeries per year was 43.1. An orbital implant was applied in 168 patients.

CONCLUSIONS

The most frequent indications for eye amputation were painful blind eye (37%) and neoplasm (34%). During the study period, the annual number of eye amputations was stable, but an increase in bulbar eviscerations was noticed. Orbital implants were used in 33% of patients in 1996 and 67% in 2003.

Stones in the lacrimal gland: a rare condition

PURPOSE

Stones (dacryoliths) in the lacrimal drainage system are relatively common. However, stones in the lacrimal gland itself are very rare. We present three cases of lacrimal gland stones and describe the clinical and histopathological characteristics and composition of the stones.

METHODS

Three patients presented with swelling in the lateral canthal region of several months' duration. Clinical examination in each case revealed a mass adjacent to the lacrimal gland. We carried out surgical excision, histological examination and Raman spectroscopy.

RESULTS

Histopathological examination of the excised material showed an eosinophilic, amorphic material organized in lamellae and localized in a ductule. The findings were consistent with a stone in the lacrimal gland in all three cases. All stones were composed of proteins of similar types. After surgery, the three patients healed without complications.

CONCLUSIONS

Lacrimal gland stones represent a very rare but relevant differential diagnosis when a patient presents with unilateral persistent conjunctivitis or with a tumour in the lateral canthus. Treatment is excision under local anaesthesia.

[Extranodal marginal zone lymphoma of the ocular adnexa]

INTRODUCTION

Lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is among the most common malignant lymphomas of the ocular adnexa and it furthermore shows an increasing incidence. The disease is most often localized and indolent of nature; gentle treatment is therefore of essence to avoid complications, especially visual impairment. MALT lymphoma can be treated with radiotherapy (RT), but in case of relapse, alternatives are required. New treatment modalities such as anti-cluster of differentiation (CD)-20 monoclonal antibodies (rituximab) and local injection of interferon-alpha have shown promising results.

MATERIAL AND METHODS

During the 2001-2006 period, nine patients with MALT lymphoma of the ocular adnexa were treated with RT at the Copenhagen University Hospital, Denmark. The visual acuity of six of the nine patients was evaluated before and after receiving RT.

RESULTS

All nine patients achieved complete remission after a total RT dose of 26 Gy. One patient relapsed after 26 months and was then successfully treated with rituximab. Furthermore, one patient experienced a striking improvement of vision after RT: from 2/60 to 6/6 in the affected eye. The visual acuity of five patients was either constant or decreased a maximum of one line on Snellen's Chart.

CONCLUSION

RT is effective in treatment of MALT lymphomas of the ocular adnexa. Rituximab showed an excellent result in one patient with recurrent disease. However, latent infections such as hepatitis B virus (HBV) should be considered before rituximab is administered.

Functional magnetic resonance imaging of the normal and abnormal visual system in early life

Functional magnetic resonance imaging (fMRI) in young children may provide information about the development of the visual cortex, and may have predictive value for later visual performance. The purpose of this study was to evaluate the usefulness of fMRI for examining cerebral processing of vision in very young infants and in infants with brain damage. We examined 15 preterm infants, 12 children suspected of having a cerebral visual impairment and 10 children with a normal visual system, all of whom were either spontaneously asleep or sedated with chloral hydrate. Cortical response to stroboscopic light stimulation could be demonstrated in all technically acceptable data sets from children with a post-menstrual age (PMA) of > 41 weeks, but not in younger infants. Children < 60 weeks PMA showed either a blood oxygenation level-dependent (BOLD) signal increase or decrease, while all older children showed a signal decrease. The activated cortical volumes showed a linear relation to age for healthy children younger than 90 weeks PMA, but were small in children with visual impairment. In two children with unilateral damage to the optic radiations, activation was strongly asymmetrical with greatest activation on the healthy side. In future prospective studies, results from the period from birth to six months of age should be interpreted with caution, as inter-individual variation of cortical development may be confused with functional deficit.

Prenatal and perinatal striatal injury: a hypothetical cause of attention-deficit-hyperactivity disorder?

Experimental data indicate a particular vulnerability of striatal neurons in the developing brain, and together with the idea that the striatum is important for context recognition and behavior, these data have led the author to search for subtle striatal lesions, in the form of biochemical changes, in children who have suffered perinatal adverse events. Evidence is presented to demonstrate that the composition of metabolites in the striatum is altered, primarily in the form of an elevated level of lactate, in human neonates who have suffered various perinatal disorders, such as germinal matrix hemorrhage, intrauterine growth retardation, and asphyxia. An elevated level of lactate suggests tissue hypoxia, which may interfere with the formation of frontostriatal circuits and may play a role in the pathogenesis of the behavioral disturbances observed in a proportion of children with a history of perinatal adverse events.

Bilateral optic neuritis in acute human immunodeficiency virus infection

PURPOSE

To report a case of acute viral disease accompanied by bilateral optic neuritis with substantial paraclinical evidence that human immunodeficiency virus was the causative agent.

METHODS

Clinical and paraclinical examination. Magnetic resonance imaging.

RESULTS

Virus and antibody titers as well as reverse lymphocytosis were consistent with acute infection by the human immunodeficiency virus-1.

CONCLUSIONS

Human immunodeficiency virus infection should be considered in the differential diagnosis of acute optic neuritis.

Neonatal seizures associated with cerebral lesions shown by magnetic resonance imaging

AIM

To determine the diagnostic potential of magnetic resonance imaging (MRI) in neonatal seizures; to elucidate the aetiology, timing, and prognosis of the cerebral lesions detected.

METHODS

Thirty one term neonates with clinical seizures underwent ultrasonography between days 1-7 (mean 2.5 days) and a high field spin-echo MRI scan on days 1-30 (mean 8.1 days), both of which were repeated at 3 months of age. Routine investigation excluded, as far as possible, infection, haematological, and metabolic-toxic causes as causes of the neonatal seizures.

RESULTS

Brain abnormality was demonstrated by MRI in 68% of infants and ultrasonographically in 10%. Diffuse brain lesions (present in 29%) were associated with high mortality (58%) and morbidity (42%), whatever the aetiology. In contrast to a better short term prognosis for neonates with focal lesions where no infants died, 33% had a handicap, and the rest were normal at a mean follow up age of 2 1/2 years. Cerebral lesions were presumed to have antepartum origin in 43% of cases. Seizure aetiology was considered to be hypoxic-ischaemic in 35%, haemorrhagic in 26%, metabolic disturbances and cerebral dysgenesis in 16% and unknown in 23%.

CONCLUSIONS

MRI detected a remarkably high incidence of brain lesions in neonatal seizures. Almost half of these were of prenatal origin and pathogenesis may essentially be attributed to hypoxic and/or haemodynamic causes.

Metabolic changes in the striatum after germinal matrix hemorrhage in the preterm infant

To investigate the metabolic consequences of germinal matrix hemorrhage (GMH) we used volume-selective 1H magnetic resonance spectroscopy in the striatal region in 12 preterm infants with predominantly small GMH. Both sides of the brain were investigated twice. Metabolite indices were calculated as the metabolite signal, recorded with TR = 1.6 s and TE = 272 ms, divided by the fully relaxed water signal corrected for transverse relaxation time constant (T2) decay. At the first investigation, when the infants were 32.5 +/- 2.0 (mean +/- SD) wk postmenstrual age, the hemorrhage was unilateral or markedly asymmetrical in size in 10 of 12 infants. The lactate index was higher (p < 0.01) and the phosphocreatine + creatine (Cr) (p < 0.05) and N-acetyl-L-aspartate (NAA) (p < 0.05) indices lower in the side with the larger hemorrhage. At the second investigation, 54.1 +/- 2.7 wk postmenstrual age, no sign of a previous GMH could be seen on magnetic resonance imaging in three of 10 infants. Lactate could be detected in two of 10 infants only, and the Cr and NAA indices did not differ between sides. However, the choline index was significantly higher in the side with the larger hemorrhage (p < 0.01). We conclude that GMH is initially followed by lactate accumulation and possibly a delay in maturation as indicated by the transiently low Cr and NAA indices. Moreover, an increased choline index at the corrected age of 3 mo indicates a more persistent metabolic change after small GMH.

The apparent diffusion coefficient of water in gray and white matter of the infant brain

PURPOSE

The purpose was to obtain normal values of the apparent diffusion coefficient (ADC) in the infant brain and to compare ADC maps with T1- and T2-weighted images.

METHOD

Diffusion was measured in nine infants with an ECG-gated SE sequence compensated for first-order motion. One axial slice at the basal ganglia level was investigated with the diffusion-encoding gradients in the slice-selection direction.

RESULTS

On ADC maps, the corpus callosum and the optic radiations appeared dark before the onset of myelination, and the crus posterior of the internal capsule could be visualized before it appeared on T1- or T2-weighted images. In gray and white matter, the mean ADC ranged from 0.95 x 10(-9) to 1.76 x 10(-9) m2/s. In the frontal and occipital white matter, in the genu corporis callosi, and in the lentiform nucleus, the ADC decreased with increasing age. The cortex/white matter ratio of the ADC increased with age and approached 1 at the age of 30 weeks.

CONCLUSION

ADC maps add information to the T1 and T2 images about the size and course of unmyelinated as well as myelinated tracts in the immature brain.

Susceptibility contrast imaging of CO2-induced changes in the blood volume of the human brain

PURPOSE

To investigate changes in the regional cerebral blood volume (rCBV) in human subjects during rest and hypercapnia by MR imaging, and to compare the results from contrast-enhanced and noncontrast-enhanced susceptibility-weighted imaging.

MATERIAL AND METHODS

Five healthy volunteers (aged 24-29 years) were studied during inhalation of atmospheric air and 7% CO2. A bolus injection of Gd-DTPA was given during the acquisition of a series of susceptibility-weighted, fast gradient echo images (TR/TE = 27/22 ms). The images were converted to delta R2* maps, and CBV was calculated pixelwise by fitting a gamma-variate function to the data. The tissue concentration vs time curves were deconvoluted using an input function obtained by arterial sampling.

RESULTS

The ratio of gray to white matter CBV (1.9-2.5) as well as the fractional increase in rCBV during hypercapnia (about 30%) was found to be in accordance with results obtained by other methods. Noncontrast functional MR (fMR) imaging showed signal increases in gray matter, but also inconsistent changes in some white matter regions.

CONCLUSION

In this experiment, contrast-enhanced imaging seemed to show a somewhat higher sensitivity towards changes in cerebral hemodynamics than noncontrast-enhanced imaging. The results of the deconvolution analysis suggested that perfusion calculation by conventional tracer kinetic methods may be impracticable because of nonlinear effects in contrast-enhanced MR imaging.

Use of brain lactate levels to predict outcome after perinatal asphyxia

Perinatal asphyxia is an important cause of neurological disability, but early prediction of outcome can be difficult. We performed proton magnetic resonance spectroscopy (MRS) and global cerebral blood flow measurements by xenon-133 clearance in 16 infants with evidence of perinatal asphyxia. Cerebral blood flow was determined daily in the first 3 days after birth in seven cases. Proton MRS was performed in 11 infants within the first week (mean 3.7 days), the rest within the first month (mean 22.2 days), and all had a scan around 3 months of age. Four infants died neonatally, three showed neurological deficits and the rest seemed to be progressing normally at neurodevelopmental follow-up at 1 year of age. A significant correlation was found between initial brain lactate levels and severe outcome (p = 0.0003) just as between cerebral hyperperfusion (mean cerebral blood flow (CBF) 86 ml(100 g)-1 min-1), (p = 0.02) and outcome. The diagnostic and prognostic implications of early MRS and CBF are predictive of poor outcome in severely asphyxiated infants.

Cerebral glucose metabolism is decreased in white matter changes in patients with phenylketonuria

Cerebral magnetic resonance imaging (MRI) has revealed white matter changes in patients with phenylketonuria (PKU), an inborn error of metabolism with increased plasma phenylalanine level. Because the significance of these lesions is unknown, this study was undertaken to determine whether glucose metabolism was depressed in cerebral white matter MRI changes in patients with PKU. Four patients with PKU and nine healthy volunteers with an average age of 23 y (range 19-26 y) and 23 y (range 20-27 y), respectively, were studied. The IQ of patients with PKU was between 58 and 97. Cerebral MRI and positron emission tomography images with 18F-deoxyglucose were obtained, and arteriovenous differences for oxygen and glucose as well as cerebral blood flow was measured simultaneously to determine global cerebral oxygen and glucose metabolism. Cerebral MRI revealed that all patients with PKU had white matter changes with characteristic localization. In patients with PKU, regional glucose metabolism was 36% lower in the anterior periventricular areas, 0.14 +/- 0.06 compared with 0.22 +/- 0.04 mumol.g-1.min-1 in controls (mean +/- SD, p < 0.05, Mann-Whitney). Further, the ratio between glucose metabolism in the affected white matter and the cortex was 14% lower in the patients, decreasing from 0.57 +/- 0.05 to 0.48 +/- 0.06 (p < 0.05). Global cerebral blood flow, oxygen and glucose consumption were similar in the two groups. In conclusion, regional glucose metabolism is lower in MRI-demonstrated white matter changes. In mildly intellectually impaired patients with PKU, global cerebral glucose and oxygen metabolism remain intact.

Volumetric analysis of the normal infant brain and in intrauterine growth retardation

Twenty-eight infants with postmenstrual ages (PMA) in the range of 32-80 weeks were investigated. Twenty were newborn; among these the observed birth weight divided by the expected weight ranged from 0.31 to 1.1. Axial magnetic resonance images were recorded with a triple spin-echo sequence and the volumes were determined by encircling each structure of interest on every slice. Segmentation into grey matter, white matter and CSF was done by semi-automatic discriminant analysis. Growth charts for the cerebrum, cerebellum, corpora striata, thalami, ventricles, and grey and white matter are provided for infants with appropriate birth weight. The striatal (P = 0.02) and thalamic (P < 0.001) percentage of the hemispheric volume decreased with age, whereas the ratio of grey matter to white matter (G/W-ratio) increased (P = 0.01). In the neonatal patients, brain volumes were independently associated with both PMA and the degree of growth retardation. It was calculated that the hemispheric volume was reduced by from 16% to 23% if the total bodyweight was reduced by 40%. The G/W-ratio was found to be independently associated with the PMA (P < 0.05) and the degree of IUGR (P < 0.1) suggesting that fetal growth retardation reduces grey matter volume more than white matter.

Cerebral energy metabolism during hypoxaemia. A 31P and 1H magnetic resonance study

By means of proton and phosphorous magnetic resonance spectroscopy at 1.5 Tesla the human cerebral metabolism was investigated during mild and moderate hypoxaemia. Seven volunteers participated and spectra were obtained while the subjects were breathing atmospheric air, 16, 12 and 10% oxygen in N2.PaO2, PCO2 and arterial oxygen saturation were determined during the spectroscopic measurements. Haemodynamic and respiratory mechanisms compensated the hypoxic condition and no lactate production was found. There was no change in N-acetyl-aspartate. No change in intracellular pH was found. A slight but non-significant decrease in PCr/P(i)-ratio was found, indicating a decrease in the phosphorylation potential of the brain in response to hypoxaemia. The brain sustains aerobic metabolism during mild to moderate hypoxaemia.

Brain lactate in preterm and growth-retarded neonates

Glucose is the predominant cerebral energy source under physiological conditions, although other substrates may support cerebral metabolism. The present study was undertaken to determine if lactate is present in the immature human brain, and if so, whether or not concentrations of lactate differ between small-for-gestational-age and appropriate-for-gestational-age infants. Thirty stable, healthy infants with normal brains were investigated. As the only nutrient, all received milk enterally prior to the investigation, which was carried out without sedation. Mean gestational age was 35 completed weeks (range 28-41 weeks) and mean birth weight was 2170 g (range 855-4100 g). Proton nuclear magnetic resonance spectra from the striatal region were obtained while the infants were sleeping quietly. Lactate was present in all 10 preterm small-for-gestational-age and 10 of 13 preterm appropriate-for-gestational-age infants, and the concentration was inversely related to postmenstrual age (p < 0.002). In addition, lactate increased with the degree of growth retardation (p < 0.01). At present the significance of lactate is unclear. Lactate may be produced locally or in peripheral tissues, and may support brain metabolism.

Signal changes in gradient echo images of human brain induced by hypo- and hyperoxia

The effect of hypoxia (inspired oxygen fraction, FiO2 of 10% and 16%) and hyperoxia (FiO2) of 100%) on gradient echo images of the brain using long echo times was investigated in six healthy volunteers (age 24-28 years). Different flip angles were used with an FiO2 of 10% to assess the importance of saturation effects. The total cerebral blood flow was measured by a phase mapping technique during normoxia as well as hypoxia (FiO2 of 10% and 16%) and hyperoxia (FiO2 of 50% and 100%). High relative signal changes were found, independently of the flip angle, with FiO2 of 10%. With a flip angle of 40 degrees the values of delta R2* for cortical grey matter, central grey matter, white matter and the sagittal sinus were 0.79, 0.41, 0.26 and 3.00/s; with a flip angle of 10 degrees the corresponding values were 0.70, 0.37, 0.24 and 3.15/s. The total cerebral blood flow increased by 41% during inhalation of 10% O2 and decreased by 27% during 100% O2; no flow changes were seen during moderate changes in FiO2. It is concluded that flow effects play a minor role for fMRI signal strength in this application since (i) they did not abolish the signal changes caused by changes in blood oxygenation during hyper- and hypoxia, (ii) the observed signal changes were closely related to the changes in arterial oxygen saturation during hypoxia and (iii) the signal changes were little affected by changing the flip angle from 40 degrees to 10 degrees.

Local vascular CO2 reactivity in the infant brain assessed by functional MRI

The local cerebral vascular response to hyperventilation was investigated in five distressed, intubated infants by means of a T2 sensitive gradient-echo MRI technique at 1.5 T. In one preterm infant, the MR signal change during hyperventilation was sparse. In four term infants, the mean MR signal of the brain slice investigated decreased by 1.2-2.6% per kPa change in PCO2 as a reflection of decreased cerebral blood flow during hyperventilation. Pixel-wise analysis revealed absence of vascular response in the basal ganglia, the thalamus or in the occipital region. In two adult controls, who hyperventilated voluntarily, the vascular reactivity was homogeneously distributed predominantly over the grey matter. The experiments demonstrate that local impairment of vascular CO2 reactivity in the distressed infant brain can be detected by T2 sensitive gradient-echo MRI, which is also known as functional MRI.

Blood-brain barrier transport of amino acids in healthy controls and in patients with phenylketonuria

Blood-brain barrier permeability to phenylalanine and leucine in four patients with phenylketonuria and in four volunteers was measured five times by the double-indicator method at increasing plasma concentrations of phenylalanine. Based on the permeability-surface area product (PS) from blood to brain (PS1) and on plasma phenylalanine levels, Vmax and the apparent Km for phenylalanine were determined. Statistically significant relationships between plasma phenylalanine and PS1 were established in three out of four volunteers, the average Vmax value being 46.7 nmol/g per min and the apparent Km 0.328 mmol/L. Owing to saturation of the carrier, such a relationship could not be established in the patients. In phenylketonuria, PS1 for phenylalanine and leucine decreased significantly by 55% and 46%, respectively. Transport from brain back to blood, PS2, decreased significantly and cerebral large neutral amino acid net uptake was generally decreased in patients with phenylketonuria. In conclusion, the transport of L-phenylalanine across the human blood-brain barrier follows Michaelis-Menten kinetics. In phenylketonuria, brain permeability to large neutral amino acids is reduced by about 50% and net uptake appears decreased.

Metabolite concentrations in the developing brain estimated with proton MR spectroscopy

The purpose of the present study was to estimate absolute concentrations and relaxation time constants of metabolites that were detectable with proton magnetic resonance (MR) spectroscopy in the healthy preterm, term, and infant brain. Five MR spectra were recorded for each infant by using STEAM (stimulated-echo acquisition mode) sequences with different TEs and TRs. Water was used as an internal standard. The T1 of choline-containing compounds (Cho) and the T1 of phosphocreatine plus creatine (PCr+Cr) decreased. The T2 of the N-acetyl-L-aspartate (NAA) resonance increased, probably because of a relatively larger signal overlap with glutamate in the most immature brains. The concentration of NAA almost doubled, whereas the Cho concentration showed only a nonsignificant tendency to decrease; therefore, the well-known increase in the ratio of NAA to Cho appears to be due mostly to an increase in NAA concentration. The concentration of PCr+Cr increased rapidly and reached adolescent values at approximately 4 months of age.

Functional MRI of CO2 induced increase in cerebral perfusion

The sensitivity of MR gradient echo imaging towards CO2 induced changes in cerebral blood flow was investigated in 10 normal subjects. The subjects were inhaling 5% and 7% CO2 and the experiments were carried out at 1.5 T (n = 6) and 2.0 T (n = 5), allowing a comparison of field strengths. Additional experiments were carried out using a higher spatial resolution. The largest signal increases were noted in areas corresponding to larger vessels, but significant changes were also conspicuous in deeper cortical and central grey matter. The changes appeared linearly related to the arterial CO2 tension, within the range of PaCO2 studied. In white matter, the changes were not statistically significant.