Search PubMed⌕ Search

Biomedical subjects

Grant T Liu

Publications and source records attributed to Grant T Liu.

At least 19 recordsLinked to original sources
PubMed2005

Near-infrared spectroscopy of the visual cortex in unilateral optic neuritis.

PURPOSE: To examine the occipital-lobe activation of patients with optic neuritis using near-infrared spectroscopy. DESIGN: Experimental study. METHODS: NIRS was performed on five patients with acute unilateral optic neuritis during monocular visual stimulation. As controls, six normal subjects were also tested in the same manner. RESULTS: In the patients with optic neuritis, the changes in the hemoglobin concentrations (oxyhemoglobin, deoxyhemoglobin, and total hemoglobin) in the occipital lobe were found to be markedly reduced when the clinically affected eyes were stimulated compared with the fellow eyes. The response induced by the stimulation of the affected eye was decreased, even when the patient's visual acuity improved to 20/20 in the recovery phase. There was no difference in the concentration changes between the two eyes in the control subjects. CONCLUSIONS: NIRS may be useful in detecting visual dysfunction objectively and noninvasively in patients with visual disturbance, especially when used at the bedside.

Adolescent↗
PubMed2005

Long-term follow-up and prognosis of orbital apex syndrome resulting from nasopharyngeal rhabdomyosarcoma.

PURPOSE: Nasopharyngeal rhabdomyosarcoma may present with a variety of ophthalmic symptoms. Direct extension of the tumor into the orbital apex can lead to ophthalmoplegia and loss of vision. The prognosis for recovery of vision and ocular motility in patients with an orbital apex syndrome due to nasopharyngeal rhabdomyosarcoma is examined. DESIGN: Retrospective case series. METHODS: Six eyes from four patients with nasopharyngeal rhabdomyosarcoma who presented to the Children';s Hospital of Philadelphia with a clinical orbital apex syndrome were identified. Complete ophthalmic examination, including visual acuity and extraocular motility at the time of presentation, was reviewed. Tumor extension into the orbital apex was confirmed radiographically. Follow-up ophthalmic evaluations were reviewed for all patients with an average follow-up of 5.5 +/- 3.1 years (range 1 to 8 years). RESULTS: Six eyes of four patients had limited ocular ductions along with marked loss of vision at presentation. All patients were treated with chemotherapy and radiation, with reduction of tumor mass. Ocular motility recovered in all patients, occurring by an average of 2.2 +/- 1.8 months after initiation of therapy. Four of six eyes had little or no recovery of visual acuity detected at long-term follow-up. CONCLUSIONS: Patients with ocular motor deficits in orbital apex syndromes caused by extension of nasopharyngeal rhabdomyosarcoma have an excellent prognosis for recovery after treatment of the tumor. The long-term prognosis for visual recovery, however, is poor.

Child, Preschool↗
PubMed2004

Acute ocular motor mononeuropathies: prospective study of the roles of neuroimaging and clinical assessment.

The role for immediate neuroimaging in patients 50 years of age or older with acute isolated third, fourth, and sixth nerve palsies is controversial. We prospectively evaluated 66 patients, aged 50 years and older (median 67 years, range 50-85), with acute isolated ocular motor mononeuropathies. Our purpose was to evaluate both the role of neuroimaging and the role of clinical assessment in determining etiology. We found that clinical features, including time to maximal diplopic symptoms, were not predictive of etiology (median 2 days to maximal diplopic symptoms for both peripheral microvascular and other etiologies). The presence of any common vascular risk factor, including diabetes mellitus, hypertension, hypercholesterolemia, or coronary artery disease, was significantly associated with peripheral microvascular etiology in this cohort (p=0.0004, Fisher's exact test). Despite the high prevalence of peripheral microvascular ischemia as an etiology in this age group, other causes were identified by magnetic resonance imaging (MRI) or computed tomography (CT) scanning in 14% of patients. Diagnoses included brainstem and skull base neoplasms, brainstem infarcts, aneurysms, demyelinating disease, and pituitary apoplexy. Neuroimaging procedures may have a role in the initial evaluation of patients 50 years of age or older with acute ocular motor mononeuropathies.

Abducens Nerve Diseases↗
PubMed2004

Optic radiation involvement in optic pathway gliomas in neurofibromatosis.

PURPOSE: Optic pathway gliomas (pilocytic astrocytomas) in neurofibromatosis type 1 (NF-1) typically involve some combination of the optic nerves, chiasm, or optic tracts. Involvement of the optic radiations is rare. DESIGN: This paper describes seven patients with NF-1 with gliomas involving the pregeniculate optic pathway in addition to the optic radiations. METHODS: A retrospective database review was made of all patients with NF-1 and optic pathway gliomas seen by one of the authors (G.T.L.) at the Children's Hospital of Philadelphia from July 1993 to October 2001. Patients with involvement of pregeniculate optic pathway and the optic radiations were identified. From November 2001 to February 2003, patients were sought prospectively. Cases were also identified from the practice of another author (M.C.B.) at Arkansas Children's Hospital. RESULTS: Four patients from Children's Hospital of Philadelphia (three of 83 total NF-1/optic pathway gliomas from July 1993 to October 2001 and one prospectively) and three from Arkansas Children's Hospital were identified. Two had expanding mass lesions within the white matter of the temporal or parietal lobes, which were histopathologically demonstrated to be pilocytic astrocytomas. The other five had radiographic involvement of the optic radiations but did not undergo biopsy. In three of the cases the vision was 20/200 or worse in each eye. CONCLUSIONS: Optic pathway gliomas in NF-1 may rarely involve the optic radiations. Optic radiation involvement may signal a more aggressive optic pathway glioma in patients with neurofibromatosis-1.

Child, Preschool↗
PubMed2004

Acquired, isolated third nerve palsies in infants with cerebrovascular malformations.

PURPOSE: To report two infants with acquired, isolated third nerve palsies attributable to intracranial cerebrovascular malformations. DESIGN: Observational case report. METHODS: Two patients are described. Each was examined in a university-based pediatric ophthalmology and neuro-ophthalmology practice. RESULTS: An 8-month-old child presented with a pupil-involving partial left third nerve palsy because of a partially thrombosed fusiform aneurysm of the left internal carotid artery. A 3-month-old infant developed a right third nerve palsy from a giant arteriovenous fistula arising from an M2 branch of the right middle cerebral artery. CONCLUSION: Patients younger than 8 months and 3 months with acquired, isolated third nerve palsies resulting from intracranial cerebrovascular malformations could not be found in a MEDLINE search. In conclusion, at even this young age, acquired, isolated third nerve palsies may be the initial manifestation of an intracranial aneurysm or fistula. Magnetic resonance imaging (MRI) and MRI-angiography were adequate for detecting these processes.

Arteriovenous Fistula↗
PubMed2004

Alexia without agraphia following biopsy of a left thalamic tumor.

Alexia without agraphia is a rare disconnection syndrome characterized by the loss of reading ability with retention of writing and verbal comprehension. We report a patient who developed alexia without agraphia after undergoing a biopsy for a malignant glioma involving the left thalamus. A 15-year-old right-handed male presented with 3 days of severe headache, and vomiting, and 1 month of blurry vision in his right visual field. Magnetic resonance imaging of the brain disclosed a large exophytic mass originating in the left thalamus, with mass effect and hydrocephalus. The patient underwent biopsy of the left thalamic mass via a transcallosal approach. Postoperatively, the patient complained of inability to read or identify letters. Examination revealed alexia without agraphia. The syndrome of alexia without agraphia can be rarely caused after surgery. A transcallosal procedure through the splenium of the corpus callosum may disrupt the visual association fibers traveling from the right occipital cortex to the left angular gyrus. In our case the syndrome occurred because of a preexisting right homonymous hemianopia resulting from a left thalamic tumor.

Adolescent↗
PubMed2003

The role of unilateral temporal artery biopsy.

PURPOSE: To examine the role of unilateral temporal artery biopsy (TAB) in suspected giant cell arteritis (GCA). DESIGN: Retrospective interventional case series. PARTICIPANTS: We identified 181 subjects from pathology and diagnostic code databases at the University of Pennsylvania Medical Center who underwent TAB between January 1990 and January 2001. METHODS: The medical records for all subjects who underwent TAB were reviewed. Follow-up information was obtained by telephone or record review for those patients who had negative unilateral TAB. MAIN OUTCOME MEASURES: Follow-up information for patients with unilateral negative TAB was reviewed for potential adverse outcomes caused by missed or delayed diagnoses of GCA. Presenting signs and symptoms and laboratory values were recorded for all subjects. Comparisons of clinical profiles between subsets of subjects were performed using Fisher's exact test, significance level alpha = 0.01. RESULTS: Follow-up information was available for 88 (86%) of 102 subjects who had unilateral negative biopsy samples. One (1%) subjects of 88 had a subsequent positive contralateral TAB; no adverse outcomes occurred for this subject or for any other subjects with unilateral negative TAB. Compared with subjects who had unilateral positive or who underwent bilateral TAB (n = 74), those who had unilateral negative TAB (n = 88) had a significantly lower prevalence of jaw claudication (P = 0.007). Compared with subjects diagnosed with GCA (n = 39), those with unilateral negative TAB (n = 88) had significantly lower frequencies of jaw claudication (P = 0.001), "chalky white" optic disc edema (P = 0.002), and fever (P < 0.0001). Compared with subjects with positive TAB (n = 33), subjects with negative TAB (n = 148) had significantly lower prevalence of jaw claudication (P < 0.0001), "chalky white" disc edema (P = 0.0002), pale disc edema (P = 0.006), or any systemic symptom other than headache (P = 0.0002). ("Chalky white" denotes notably extreme disc pallor). The most common indications for biopsy in subjects with unilateral negative TAB were elevated erythrocyte sedimentation rate (ESR) (74%), headache (69%), visual complaints (58%), and ophthalmic signs (52%). Although ESR was a significant predictor of positive TAB overall (unilateral and bilateral TAB) in logistic regression models accounting simultaneously for subject age (P = 0.04), ESR did not significantly predict unilateral negative status in our patients (P = 0.13). CONCLUSIONS: In this cohort of patients, unilateral TAB was associated with an extremely low frequency (1%) of subsequent positive contralateral TAB and was not associated with adverse visual or neurologic outcomes for any subject. We conclude that in the hands of experienced physicians, a unilateral TAB is sufficient to exclude a diagnosis of GCA in populations for which clinical suspicion is low. Jaw claudication, pale optic disc edema, particularly "chalky white" disc edema, fever, or any systemic symptom other than headache should raise suspicion for a diagnosis of GCA.

Biopsy↗
PubMed2003

Pituitary apoplexy causing optic neuropathy and horner syndrome without ophthalmoplegia.

A 47-year-old woman presented with headache, acute monocular vision loss, and ipsilateral Horner syndrome. Apart from the optic neuropathy, all cranial nerve function was intact. Magnetic resonance imaging revealed an enlarged pituitary gland with compression of the orbital apex. The surgical specimen was consistent with pituitary apoplexy. The combination of headache, acute visual loss, and ipsilateral Horner syndrome without ophthalmoplegia, which may suggest carotid artery dissection, is evidently an unusual manifestation of pituitary apoplexy.

Anti-Inflammatory Agents↗
PubMed2003

Laser pointer visual field screening.

BACKGROUND: Sensitivity of confrontation visual field (CVF) screening is low unless defects are significant. We compared the sensitivity of laser pointer visual field screening (LVF) with conventional CVF for identifying eyes with abnormal automated perimetry. METHODS: Ninety consecutive patients presenting for HVF prospectively underwent a masked comparison of CVF and LVF testing (175 eyes) from April to May 2000. LVF was performed using a laser pointer target projected onto a tangent screen. Points were tested in random fashion on either side of the vertical and horizontal meridians, near central fixation, around the blind spot, and in each quadrant. Single and double simultaneous finger counting was used to test CVF. RESULTS: LVF demonstrated significantly greater sensitivity as compared with CVF (73% versus 31%, P = 0.001) in identifying field defects found on HVF. Specificities for LVF and CVF were 82% and 99%, respectively. The average testing times per eye were 0.5 minute for CVF, 1.5 minutes for LVF, and 8.0 minutes for HVF. CONCLUSIONS: In this cohort, laser visual field testing was significantly more sensitive than confrontation testing. It may represent an effective, time-efficient tool for visual field screening.

Cohort Studies↗
PubMed2002

Eye dominance in the visual cortex using functional MRI at 1.5 T: an alternative method.

PURPOSE: To develop a functional MRI method for producing eye dominance histograms in humans at 1.5 Tesla (T). METHODS: In the first set of experiments, 8 normal persons were tested. The eye dominance of each voxel within the person's visually activated primary visual cortex was determined with Student t statistics during a left eye versus right eye contrast. Eye dominance distribution was plotted, and the mean t statistic was used to describe the histogram asymmetry. In the second set of experiments, the effect of monocular optical blur and decreased luminance via filter was studied, and eye dominance distributions were similarly determined. RESULTS: The eye dominance histogram in each of the 8 normals was approximately symmetric; the average mean t value was +0.13. All 4 subjects with the right eye blurred had histograms approximately symmetric or slightly shifted toward the left eye (average mean t = +0.56), and all 4 subjects with the right eye filtered had histograms dramatically shifted toward the left eye (average mean t = +2.22). The average mean t for the group with the right eye filtered was significantly different from that of the other 2 groups (P <.0001). CONCLUSIONS: With noninvasive methods in normal persons, functional magnetic resonance imaging techniques at 1.5 T were able to characterize the distribution of eye dominance of voxels in primary visual cortex, based upon their t statistic in the left eye versus right eye contrast. The method is sensitive to filtering but relatively insensitive to visual blur. This approach may have a future use in the study of amblyopia in humans.

Adolescent↗
PubMed2002

Orbital neural-glial hamartoma associated with a congenital tonic pupil.

Tonic pupils in children are rare, and only a handful of reports exist in the literature. We present the case of an orbital neural-glial hamartoma in an infant with a congenital tonic pupil and no proptosis. We have previously described this association in another child. This new case, the 6-year follow-up from the previous case, and a discussion of tonic pupils are presented.

Hamartoma↗
PubMedDate not supplied

Effects of voxel size on detection of lateral geniculate nucleus activation in functional magnetic resonance imaging.

PURPOSE: To study the effect of voxel size on the detection of lateral geniculate nucleus (LGN) activation during visual stimulation using functional magnetic resonance imaging (fMRI) at 1.5 T. METHODS: Ten normal subjects were scanned during visual stimulation with flashing goggles, four times, with four different voxel sizes. The data were spatially normalized, and LGN activation was identified in the standard coordinates in each subject. RESULTS: When the statistical analysis was performed without global normalization, activation of LGN was detected in both hemispheres in all subjects. However, when global normalization was used, activation of LGN was found in only six subjects in whom the activation could be most frequently detected at the smallest voxel size. CONCLUSIONS: Our results suggest that LGN activation can be observed within the range of spatial resolution commonly used in conventional fMRI studies, although postprocessing may affect the detectability of LGN activation in fMRI. These findings may be useful in studying LGN activity in patients with visual disturbance.

Adolescent↗
PubMedDate not supplied

A childhood cavernous conundrum.

A 9-year-old boy presented with a left-sided "tooth ache." Subsequently, he developed new onset vertical diplopia. He was found to have a left cranial nerve three palsy. Cranial magnetic resonance imaging showed bilateral cavernous sinus lesions that were initially interpreted as possible "cavernous sinus thrombosis." Subsequent blood smear and bone marrow biopsy disclosed Burkitt lymphoma. He was treated with chemotherapy and made a dramatic recovery. Burkitt lymphoma rarely presents with a third nerve palsy but should be considered in the differential diagnosis of childhood cavernous sinus syndrome.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

Primary central nervous system angiitis, amyloid angiopathy, and Alzheimer's pathology presenting with Balint's syndrome.

We report a patient who presented with Balint's syndrome as a manifestation of primary central nervous system angiitis. Clinical findings included simultanagnosia, optic ataxia, and optic apraxia. Pathologic evaluation demonstrated amyloid angiopathy and Alzheimer's plaques. The presence of primary central nervous system angiitis along with amyloid angiopathy and Alzheimer's plaques may not be coincidental. Angiitis may be a foreign body reaction to A4 amyloid deposition.

Aged↗
PubMedDate not supplied

Functional magnetic resonance imaging and its clinical utility in patients with visual disturbances.

Functional magnetic resonance imaging (fMRI) is a powerful, non-invasive technique for mapping human brain function. Because of the robust signal intensity changes associated with visual stimuli, fMRI is particularly useful for studying visual cortex (including both striate and extrastriate cortex). Also, activation of the lateral geniculate nuclei has been successfully demonstrated by fMRI. Therefore, fMRI may be potentially useful in patients with visual deficits by providing a non-invasive method for assessing the afferent visual pathways and higher cortical areas. Although there have been several reviews on fMRI, few have highlighted its clinical applicability in patients with visual disturbances. Our article will review fMRI principles and methodology, then focus on the possible applications and limitations of this technique in clinical ophthalmology.

Humans↗
PubMedDate not supplied

Decreased activation of the lateral geniculate nucleus in a patient with anisometropic amblyopia demonstrated by functional magnetic resonance imaging.

Although postmortem morphological changes in the lateral geniculate nucleus (LGN) have been reported in human amblyopia, LGN function during monocular viewing by amblyopic eyes has not been documented in humans. We used functional magnetic resonance imaging (fMRI) to study monocular visual activation of the LGN in a patient with anisometropic amblyopia. Four normal subjects, a patient with optic neuritis and a patient with anisometropic amblyopia were studied with fMRI at 1.5 T during monocular checkerboard stimulation. Activated areas in the LGN and visual cortex were identified after data processing (motion correction and spatial normalization) with SPM99. In the 4 normal subjects, comparable activation of the LGN and visual cortex was obtained by stimulation of either the right or left eye. In the patient with unilateral optic neuritis, activation of the LGN and visual cortex was markedly decreased when the affected eye was stimulated. Similarly, decreased activation of the LGN as well as the visual cortex by the affected eye was demonstrated in the patient with anisometropic amblyopia. Our preliminary results suggest that activation of the LGN is diminished during monocular viewing by affected eyes in anisometropic amblyopia. fMRI appears to be a feasible method to study LGN activity in human amblyopia.

Adolescent↗