Transsynaptic degeneration in the visual system; report of a case

Ganglion Cell Topography Indicates Pre- or Postnatal Damage to the Retro-Geniculate Visual System, Predicts Visual Field Function and May Identify Cerebral Visual Impairment in Children - A Multiple Case Study

In this paper, we quantify the degree of ganglion cell layer thinning due to retrograde trans-synaptic degeneration (RTSD) from retro-geniculate damage in six cases who had homonymous visual field defects known since childhood. Three had prenatal injuries, occurring close to mid-gestation and in the first parts of the early and late third trimester, respectively, and representing injuries at different early developmental stages. Three had later acquired injuries, at age 1.5, 4 and 13 years. The impact of the injury to the optic radiations was revealed by fibre tractography. The ganglion cell thinning corresponded with the visual field defects and the extent and location of the primary brain damage. The most important sign of RTSD was asymmetry of the ganglion cell topography within the macular area.

Homonymous quadrantic macular ganglion cell complex loss as a sign of trans-synaptic degeneration from occipital lobe lesion

Purpose

to describe a patient with visual field (VF) defect from an occipital lobe lesion that was found to have macular ganglion cells complex (GCC) quadrantic reduction without significant peripapillary retinal nerve fiber layer (RNFL) loss on optical coherence tomography (OCT). To emphasize that macular GCC loss may be the major ocular manifestation of trans-synaptic optic pathway degeneration in occipital lobe lesions.

Observations

A 15-year-old female was investigated after a VF examination revealed a right homonymous inferior quadrantanopia. Fundoscopic examination was completely normal as were the peripapillary retinal nerve fiber layer (RNFL) thickness measurements on OCT. Macular thickness measurements however, revealed superior homonymous quadrantic GCL reduction evidencing retinal neuronal loss in direct correspondence with her VF defect. Magnetic resonance imaging showed a localized left occipital lobe gliotic lesion as the explanation for her VF defect.

Conclusions and Importance

Small post-geniculate optic pathway lesions may lead to retrograde trans-synaptic degeneration that can be detected on OCT-measured macular GCL measurements despite normal peripapillary RNFL estimates. Awareness of such occurrence in important to avoid diagnostic confusion with other anterior visual pathway diseases.

Macular Ganglion Cell Layer and Peripapillary Retinal Nerve Fibre Layer Thickness in Patients with Unilateral Posterior Cerebral Artery Ischaemic Lesion: An Optical Coherence Tomography Study

The purpose of this study is to evaluate the macular ganglion cell layer (GCL) and peripapillary retinal nerve fibre layer (RNFL) thickness in patients with unilateral posterior cerebral artery (PCA) ischaemic lesions using spectral-domain optical coherence tomography (SD-OCT). A prospective, case-control study of patients with unilateral PCA lesion was conducted in the neuro-ophthalmology clinic of Centro Hospitalar Lisboa Central. Macular and peripapillary SD-OCT scans were performed in both eyes of each patient. Twelve patients with PCA lesions (stroke group) and 12 healthy normal controls were included in this study. Peripapillary RNFL comparison between both eyes of the same subject in the stroke group found a thinning in the superior-temporal (p = 0.008) and inferior-temporal (p = 0.023) sectors of the ipsilateral eye and nasal sector (p = 0.003) of the contralateral eye. Macular GCL thickness comparison showed a reduction temporally in the ipsilateral eye (p = 0.004) and nasally in the contralateral eye (p = 0.002). Peripapillary RNFL thickness was significantly reduced in both eyes of patients with PCA compared with controls, affecting all sectors in the contralateral eye and predominantly temporal sectors in the ipsilateral eye. A statistically significant decrease in macular GCL thickness was found in both hemiretinas of both eyes of stroke patients when compared with controls (p < 0.05). This study shows that TRD may play a role in the physiopathology of lesions of the posterior visual pathway.

Sectoral analysis of the retinal nerve fiber layer thinning and its association with visual field loss in homonymous hemianopia caused by post-geniculate lesions using spectral-domain optical coherence tomography

Purpose

To report a sectoral analysis of circumpapillary retinal nerve fiber layer (cpRNFL) thinning and its association with visual field loss using spectral-domain optical coherence tomography (SD-OCT) in patients with homonymous hemianopia following acquired post-geniculate visual pathway damage.

Patients and methods

Seven patients with homonymous hemianopia due to unilateral acquired post-geniculate visual pathway lesions were studied. The average duration from the onset of brain lesions to the initial visit was 49.8 months. Forty-nine normal control subjects without visual field defects, as confirmed using a Humphrey visual field analyzer, were also enrolled. Measurement of the cpRNFL thickness was performed at the initial visit and 24 months using SD-OCT (RTVue-100® OCT). The cpRNFL thickness was divided into eight sectors (superior temporal: ST, temporal upper: TU, temporal lower: TI, inferior temporal: IT, inferior nasal: IN, nasal lower: NL, nasal upper: NU, superior nasal: SN). The eye on the same side as the occipital lobe lesions was defined as the ipsilateral eye, and the eye on the opposite side was defined as the contralateral eye.

Results

The average cpRNFL thickness in the homonymous hemianopic eyes was significantly reduced as compared with that seen in the normal controls, except for the ipsilateral eyes at the initial visit. Four of the eight sectors of the cpRNFL thickness in the homonymous hemianopic eyes were significantly reduced compared with that noted in the normal controls. In the ipsilateral eyes, the cpRNFL thickness in the ST, TU, TL, and IT sectors was significantly reduced at both the initial visit and 24 months. In the contralateral eyes, the cpRNFL thickness in the TU, TL, IT, and SN sectors was significantly reduced at both the initial visit and 24 months. The reduction of the quadrantic cpRNFL thickness significantly correlated with some of the visual field parameters, in accordance with the structure–function relationship. In the contralateral eyes, the T and I quadrant cpRNFL thickness correlated with the mean deviation and hemianopic field total deviation at 24 months. In the ipsilateral eyes, the S, T, and I quadrant cpRNFL thickness correlated with mean deviation. However, there were no correlations between the cpRNFL thickness and visual field parameters at the initial visit.

Conclusions

A reduction of the cpRNFL thickness corresponding to the hemianopic visual field loss due to acquired post-geniculate visual pathway lesions was detected using SD-OCT, and the change was more evident at 24 months than at the initial visit. The latter finding suggests that this change is, at least partially, caused by transsynaptic retrograde degeneration.

Long-term effect of retinal ganglion cell axotomy on the histomorphometry of other cells in the porcine retina

PURPOSE

To determine the effect of retinal ganglion cell axotomy on the thickness of inner plexiform, inner nuclear, and outer plexiform layers, as well as the densities of short- and middle-to-long-wavelength cones, in the porcine retina.

METHODS

Unilateral retinal ganglion cell axotomy was performed in seven domestic pigs by either surgical optic nerve section or peripapillary argon laser photocoagulation. Damage to the retinal vasculature was ruled out with fluorescein angiography. Histologic examination of the retinal tissue was performed nine months later. Cone densities were determined immunohistochemically with the anti-visual pigment antibodies COS-1 and OS-2. Image analysis of semithin retinal cross sections was used to measure the thickness of the retinal layers. The effect of axotomy was quantified by optic nerve axon counts and estimations of retinal ganglion cell counts. The data were compared between the eyes with axotomy and the contralateral normal eye using the nonparametric Wilcoxon rank sum test.

RESULTS

Treatment of the peripapillary retina with the argon laser resulted in a median decrease in axon counts and retinal ganglion cell density estimates of 31%. No optic nerve axons and cells resembling retinal ganglion cells were found in the eyes with transected optic nerves. There was no significant difference in either the thickness of any retinal layers or cone densities between axotomized and normal control eyes.

CONCLUSION

No signs of retrograde transsynaptic degeneration were observed in porcine retinas nine months after retinal ganglion cell axotomy.

Evidence for greater sight in blindsight following damage of primary visual cortex early in life

This review compares the behavioral, physiological and anatomical repercussions of lesions of primary visual cortex incurred by developing and mature humans, monkey and cats. Comparison of the data on the repercussions following lesions incurred earlier or later in life suggests that earlier, but not later, damage unmasks a latent flexibility of the brain to compensate partially for functions normally attributed to the damaged cortex. The compensations are best documented in the cat and they can be linked to system-wide repercussions that include selected pathway expansions and neuron degenerations, and functional adjustments in neuronal activity. Even though evidence from humans and monkeys is extremely limited, it is argued on the basis of known repercussions and similarity of visual system organization and developmental sequence, that broadly equivalent repercussions most likely occur in humans and monkeys following early lesions of primary visual cortex. The extant data suggest potentially useful directions for future investigations on functional anatomical aspects of visual capacities spared in human patients and monkeys following early damage of primary visual cortex. Such research is likely to have a substantial impact on increasing our understanding of the repercussions that result from damage elsewhere in the developing cerebral cortex and it is likely to contribute to our understanding of the remarkable ability of the human brain to adapt to insults.

Evidence for transneuronal degeneration in the spinal cord in man: a quantitative investigation of neurons in the intermediate zone after long-term amputation of the unilateral upper arm

Does transneuronal degeneration occur in the neurons of the spinal intermediate zone following degeneration of the anterior horn cells in man? To investigate this possibility, we carried out a quantitative examination of neurons in the cervical intermediate zone of a 56-year-old man who had suffered accidental amputation of the right upper arm 38 years prior to death. Recently, we reported that the cervical anterior horn cells of this patient were reduced in number not only on the amputation side but also on the spared side. The present study revealed that medium-sized neurons in the cervical intermediate zone, which were considered to be internuncial neurons, were decreased in number on both the amputation and the spared sides, but less so on the spared side. These findings indicate that retrograde transneuronal degeneration occurs in the internuncial neurons following degeneration of the anterior horn cells caused by amputation. Sequentially to this, degeneration of the commissural neurons in the intermediate zone secondary to that of the internuncial neurons may induce degeneration of the neurons in the intermediate zone and the anterior horn cells on the spared side.

Retinal ganglion cell degeneration following loss of postsynaptic target neurons in the dorsal lateral geniculate nucleus of the adult cat

Kainic acid was used to produce selective degeneration of neurons in the dorsal lateral geniculate nucleus of the adult cat. This degeneration mimics the rapid loss of geniculate neurons seen after visual cortex ablation in the neonate. Following survivals of 2, 4, or 6 months, the geniculate was injected with horseradish peroxidase and the retinae were examined for the presence of retrogradely labeled cells. Analysis of ganglion cell density in peripheral nasal retina revealed a 58% loss of cells overall at 6 months. The proportion of cells labeled with horseradish peroxidase decreased more rapidly, until none were labeled at 6 months. Separate analysis of small, medium, and large ganglion cell populations revealed that only medium-sized cells were lost at 2 months whereas both medium and large cells were lost at 4 and 6 months. By 6 months, 92% of medium cells and 65% of large cells had degenerated. These results show that mature retinal ganglion cells in the cat maintain a dependence on target integrity for their continued survival. When the appropriate target is lost, the ganglion cells respond first by axon terminal retraction and then by cell death.

Response of retinal terminals to loss of postsynaptic target neurons in the dorsal lateral geniculate nucleus of the adult cat

We have used the neurotoxin kainic acid to produce rapid degeneration of neurons in the dorsal lateral geniculate nucleus (dLGN) of the adult cat. This degeneration mimics the rapid loss of geniculate neurons seen after visual cortex ablation in the neonate. Subsequent anterograde transport of horseradish peroxidase injected into the eye was used to reveal the projection patterns of retinal ganglion cell axons at different survival periods after the kainic acid injection. The density of retinal projections to the degenerated regions of the geniculate was reduced considerably at 4 and 6 months survival, but at 2 months was not significantly different from normal. The laminar pattern of projections to degenerated regions of the geniculate did not change in any animals studied, even when an adjacent lamina contained surviving cells. Electron microscopic examination of degenerated dLGN revealed intact retinal (RLP) and RSD terminals at all survival times, although the density of terminals appeared much reduced when compared to controls. Some RLP terminals exhibited the "dark reaction" of degeneration and these degenerating terminals were most numerous at 2 months survival. These findings demonstrate that, in response to degeneration of their usual target cells, mature retinal ganglion cells with withdraw their axon terminals from these regions of degeneration. We conclude that mature retinal ganglion cells continue to be dependent on target integrity for the maintenance of a normal axonal arborization.

Parameters affecting the loss of ganglion cells of the retina following ablations of striate cortex in primates

Partial lesions of striate cortex were made in newborn and adolescent or young adult macaque monkeys, one newborn squirrel monkey, and adult squirrel and owl monkeys. After survival times ranging from 3 1/2 weeks to 8 years, the retinas were examined for transneuronal retrograde ganglion cell loss and retinal projections to the dorsal lateral geniculate nucleus, and other targets were examined for changes. After lesions in infant macaque monkeys and long postoperative survivals, nearly 80% of the ganglion cells were lost in the altered portions of the retinas. The degeneration appeared to be exclusively of ganglion cells projecting to the parvocellular layers of the lateral geniculate nucleus, and the loss of this class of cell appeared to be complete or nearly complete for the affected portions of the retina. Cases with shorter survivals showed that nine-tenths of the potential loss occurred within 6 months, and about half of the potential loss took place within one month. In cases where lesions were placed in adolescent and young adult macaque monkeys, the loss also was of ganglion cells projecting to the parvocellular layers. However, the rate of cell loss was slower so that little or no cell loss was apparent after six months, and only one-third to three-fourths of the potential loss occurred within 12-14 months. A cell loss of 22% was measured in the altered portions of the retina of a squirrel monkey lesioned as an infant and surviving for 6 months, but no regions of ganglion cell loss were apparent in the retinas of owl and squirrel monkeys lesioned as adults and surviving as long as two or more years. We conclude that nearly 80% of the ganglion cells project to the parvocellular layers in macaque monkeys, and that the ultimate survival of these ganglion cells depends on the presence of target neurons in the parvocellular layers. Age is important in that the loss of ganglion cells proceeds rapidly in infant macaque monkeys, but slowly in older animals. Infant New World monkeys, judging from one squirrel monkey, are also susceptible to ganglion cell loss, although apparently at a rate comparable to older macaque monkeys. Finally, adult New World monkeys do not appear to be susceptible to ganglion cell loss. These age and species differences in rates of loss and susceptibility to loss challenge a "sustaining collateral" hypothesis proposed earlier (Weller et al., 1979), and suggest alternatives and modifications.

Congenital blindness, porencephaly, and neonatal thrombocytopenia: a report of four cases

Four unrelated infants with neonatal thrombocytopenia associated with congenital blindness and porencephaly have been seen over an 18-year period. The association of congenital blindness with neonatal thrombocytopenia has not previously been reported. All children had clinical purpura in the neonatal period; in three cases, thrombocytopenia was confirmed, while in one case, the diagnosis of thrombocytopenia was presumptive; in two cases, there was evidence of circulating maternal serum platelet isoantibodies. Extensive investigation for intrauterine infection was negative in the three cases with confirmed thrombocytopenia. The thrombocytopenia resolved spontaneously after the neonatal period. It is postulated that the porencephalies were the consequence of prenatal cerebrovascular episodes. The etiology of the optic atrophy is unclear. Serial cranial ultrasound investigation is recommended for all neonates with thrombocytopenia, even if neurologically asymptomatic in the neonatal period, and serial prenatal cranial ultrasound investigation is recommended for infants of mothers with a history of having previously had infants with neonatal isoimmune thrombocytopenia.

Role of target tissue in regulating the development of retinal ganglion cells in the albino rat: effects of kainate lesions in the superior colliculus

Kainic acid or ibotenic acid was injected unilaterally into the major target regions of the axons of retinal ganglion cells--the superior colliculus (SC) or dorsal lateral geniculate nucleus (DLG)--of rat pups ranging in age from postnatal day 0 to postnatal day 10 (P0 - P10). While the collicular or geniculate neurons within the injection site died within 48 hours of the injection, damage to axons and terminals of extrinsic origin within the injected region was not apparent. The neuronal degeneration induced by the neurotoxins, observed at both the light and electron microscopic levels, resembled the neuronal degeneration that occurs in the colliculus during normal development. Macrophages were identified in the regions containing degenerating cells. Two to three weeks after the injections of neurotoxin, massive injections of the enzyme, horseradish peroxidase (HRP), were made into the retinorecipient nuclei. After about 24-hour survival time the numbers of retinal ganglion cells were estimated by counting the number of neurons containing HRP reaction products in sample areas distributed in a regular rectangular array across the entire retinal surface. In the animals in which the neurotoxin was injected into the SC during the first 4 postnatal days, there was a substantial reduction (on average 41.5%; the range: 27.5-65.5%) in the normal number (mean value of 113,000--Potts et al.: Dev. Brain Res. 3:481-486, '82) of retinal ganglion cells surviving the period of "naturally occurring ganglion cell death" in the retinae contralateral to the injected SC. By contrast, injections of neurotoxins into the DLG and/or the optic tract of newborn rats did not result in a significant reduction in the numbers of retinal ganglion cells surviving the period of naturally occurring ganglion cell death. The period of sensitivity of retinal ganglion cells to the injection of neurotoxin into the colliculi extends from birth to about the end of the first postnatal week; the greatest sensitivity seems to be restricted to the first 3-4 postnatal days. In the retinae in which the total number (and density) of ganglion cells was substantially reduced by the selective destruction of their target cells, the centro-peripheral difference in the somal diameters of the ganglion cells (apparent in normal animals) was abolished, both amongst the whole population of ganglion cells and amongst the ganglion cells with the largest somata, relatively thick axons, and large-gauge primary dendrites (Class I cells). The number and distribution of the Class I cells in the depleted retinae were, however, unaltered.(ABSTRACT TRUNCATED AT 400 WORDS)

Direct demonstration of transsynaptic degeneration in the human visual system: a comparison of retrograde and anterograde changes

Transneuronal degeneration of retinal ganglion cells was directly demonstrated in a patient who had unilateral removal of the striate cortex forty years prior to necropsy. For comparison, another case is presented showing anterograde transneuronal atrophy forty years after enucleation of one eye.

The interpretation of the degenerative changes in the intralaminar nuclei of the thalamus

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TRANS-SYNAPTIC RETROGRADE DEGENERATION IN THE VISUAL SYSTEM OF PRIMATES

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An experimental study of the relation between the medial mamillary nucleus and the cingulate cortex

The cellular changes in the mamillary nuclei following lesions of the cingulate cortex, the anterior thalamic radiation and the anterior thalamic nuclei have been studied in rabbits varying in age from 10 days to young adults. Distinct cellular degeneration ranging in severity from slight cell shrinkage to complete cell loss occurs in the medial and supra-mamillary nuclei subsequent to the retrograde changes in the anterior thalamic nuclei. The severity of this ‘retrograde transneuronal degeneration’ is a function of the age of the animal at the time of operation and of the post-operative survival period. With the aid of this technique, it has been shown that the caudal part of the pars anterior and the ventro-lateral two-thirds of the pars medialis of the medial mamillary nucleus project to the antero-medial nucleus of the thalamus, the pars basalis to the antero-dorsal nucleus and the pars posterior to the antero-ventral nucleus. No changes were observed in the lateral mamillary nucleus in any of the experiments.