On retinal hemorrhages in general:
"The cause is most likely VENOUS CONGESTION. The fetal head is compressed two to four times more forcefully than other fetal parts during the second stage of labor. Retinal hemorrhage is more common in promiparus deliveries and after forceps or vacuum extraction; it is rare after cesarean section. It may occur in normal deliveries."
 

Perimacular retinal folds from childhood head trauma
BMJ  2004;328:754-756 (27 March), doi:10.1136/bmj.328.7442.754
P E Lantz, associate professor1, S H Sinal, professor2, C A Stanton, associate professor1, R G Weaver, Jr, associate professor3
 Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA, 2 Department of Paediatrics, Wake Forest University School of Medicine, 3 Department of Ophthalmology, Wake Forest University School of Medicine

No abstract available but in summary it is a case report of a 14month old child with retinal changes often described as pathognomonic for NAI, but where the cause was clearly documented to be accidental (A television fell on the child's head).  This publication comes at a time when the expert medical evidence for child abuse is coming under increasing scrutiny following the publicity around Roy Meadows cases in the UK. The Editorial (below) is worth reading if ever you might find yourself in the witness stand. MIKE


Editorial -  The evidence base for shaken baby syndrome
BMJ  2004;328:719-720 (27 March)

We need to question the diagnostic criteria

The phrase "shaken baby syndrome" evokes a powerful image of abuse, in which a carer shakes a child sufficiently hard to produce whiplash forces that result in subdural and retinal bleeding. The theory of shaken baby syndrome rests on core assumptions: shaking is always intentional and violent; the injury an infant receives from shaking is invariably severe; and subdural and retinal bleeding is the result of criminal abuse, unless proved otherwise.1 These beliefs are reinforced by an interpretation of the literature by medical experts, which may on occasion be instrumental in a carer being convicted or children being removed from their parents. But what is the evidence for the theory of shaken baby syndrome?

Retinal haemorrhage is one of the criteria used, and many doctors consider retinal haemorrhage with specific characteristics pathognomonic of shaking. However, in this issue Patrick Lantz et al examine that premise (p 754) and conclude that it "cannot be supported by objective scientific evidence."2 Their study comes hard on the heels of a recently published review of the literature on shaken baby syndrome from 1966 to 1998, in which Mark Donohoe found the scientific evidence to support a diagnosis of shaken baby syndrome to be much less reliable than generally thought.3

Shaken baby syndrome is usually diagnosed on the basis of subdural and retinal haemorrhages in an infant or young child,1 although the diagnostic criteria are not uniform, and it is not unusual for the diagnosis to be based on subdural or retinal haemorrhages alone.w1 The website of the American Academy of Ophthalmology states that if the retinal haemorrhages have specific characteristics "shaking injury can be diagnosed with confidence regardless of other circumstances."4 Having reviewed the evidence base for the belief that perimacular folds with retinal haemorrhages are diagnostic of shaking, Lantz et al were able to find only two flawed case-control studies, much of the published work displaying "an absence of... precise and reproducible case definition, and interpretations or conclusions that overstep the data."2 Their conclusions are remarkably similar to those of Donohoe, who found that "the evidence for shaken baby syndrome appears analogous to an inverted pyramid, with a very small database (most of it poor quality original research, retrospective in nature, and without appropriate control groups) spreading to a broad body of somewhat divergent opinions."3 His work entailed searching the literature, using the term "shaken baby syndrome" and then assessing the methods of the articles retrieved, using the tools of evidence based inquiry. Reviewing the studies achieving the highest quality of evidence rating scores, Donohoe found that "there was inadequate scientific evidence to come to a firm conclusion on most aspects of causation, diagnosis, treatment, or any other matters," and identified "serious data gaps, flaws of logic, inconsistency of case definition."3

The conclusions of Lantz et al and of Donohoe make disturbing reading, because they reveal major shortcomings in the literature relating to a field in which the opportunity for scientific experimentation and controlled trials does not exist, but in which much may rest on interpretation of the medical evidence.5

If the concept of shaken baby syndrome is scientifically uncertain, we have a duty to re-examine the validity of other beliefs in the field of infant injury. The recent literature contains a number of publications that disprove traditional expert opinion in the field. A study of independently witnessed low level falls showed that such falls may prove fatal, causing both subdural and retinal bleeding.6 w2 A biomechanical analysis validates that serious injury or death from a low level fall is possible and casts doubt on the idea that shaking can directly cause retinal or subdural haemorrhages.7 w3 An important lucid interval may be present in an ultimately fatal head injury in an infant.8 Neuropathological studies have shown that abused infants do not generally have severe traumatic brain injury and that the structural damage associated with death may be morphologically mild.9 10 What is the relevance of the craniocervical injuries to corticospinal tracts, dorsal nerve roots, and so on that have been described?10 11 We do not know. What is the force necessary to injure an infant's brain? Again, we do not know.

While most abused children indisputably show the signs of violence, not all do. No one would be surprised to learn that a fall from a two storey building or involvement in a high speed road traffic crash can cause retinal and subdural bleeding, but what is the minimum force required? "It is one thing clearly to state that a certain quantum of force is necessary to produce a subdural hematoma; it is quite another to use examples of obviously extreme force... and then suggest that they constitute the minimum force necessary."12

Research in the area of injury to infants is difficult. Quality evidence may need to be based on finite element modelling from data on infants' skulls, brains, and neck structures, rather than living animals. Any studies on immature animal models, if performed, will need to be validated against the known mechanical properties of the human infant. Pending completion of such studies, the reviews by Lantz and Donohoe are a valuable contribution and provide a salutary check for anyone wishing to cite the literature in support of an opinion. Their criticisms of lack of case definition or proper controls can be levelled at the whole literature on child abuse. If the issues are much less certain than we have been taught to believe, then to admit uncertainty sometimes would be appropriate for experts. Doing so may make prosecution more difficult, but a natural desire to protect children should not lead anyone to proffer opinions unsupported by good quality science. We need to reconsider the diagnostic criteria, if not the existence, of shaken baby syndrome.

J F Geddes, retired (formerly reader in clinical neuropathology, Queen Mary, University of London)

London (j.f.geddes@doctors.org.uk)

J Plunkett, forensic pathologist

 

Central Retinal Vein Occlusion Last Updated: June 26, 2001   Synonyms and related keywords: nonischemic central vein occlusion, partial, incomplete, imminent, threatened, incipient, impending, perfused, venous statis retinopathy, ischemic central vein occlusion, complete, hemorrhagic, nonperfused   AUTHOR INFORMATION Section 1 of 10    Author Information Introduction Clinical Differentials Workup Treatment Follow-up Miscellaneous Pictures Bibliography   Author: Lakshmana M Kooragayala, MD, Staff Physician, Assistant Professor of Ophthalmology, Department of Ophthalmology, Louisiana State University Health Sciences Center at Shreveport   Lakshmana M Kooragayala, MD, is a member of the following medical societies: Louisiana State Medical Society   Editor(s): Vytautas A Pakainis, MD, Chief of Ophthalmology, Dorn Veterans Administration Medical Center, Professor of Ophthalmology, Ophthalmology, University of South Carolina School of Medicine; Donald S Fong, MD, MPH, Assistant Clinical Professor of Ophthalmology, UCLA School of Medicine; Consulting Physician, Department of Ophthalmology, Southern California Permanente Medical Group; Steve Charles, MD, Director of Charles Retina Institute; Clinical Professor, Department of Ophthalmology, University of Tennessee College of Medicine; Lance L Brown, OD, MD, Ophthalmologist, Regional Eye Center, Affiliated With Freeman Hospital and St John's Hospital, Joplin, Missouri; and Hampton Roy, Sr, MD, Clinical Associate Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences   INTRODUCTION Section 2 of 10    Author Information Introduction Clinical Differentials Workup Treatment Follow-up Miscellaneous Pictures Bibliography   Background: Central retinal vein occlusion (CRVO) is a common retinal vascular disorder. Clinically, CRVO presents with variable visual loss; the fundus may show retinal hemorrhages, dilated tortuous retinal veins, cotton-wool spots, macular edema, and optic disc edema. In view of the devastating complications associated with the severe form of CRVO, a number of classifications were described in the literature. All these classifications take into account the area of retinal capillary nonperfusion and development of neovascular complications. Broadly, CRVO can be divided into 2 clinical types, ischemic and nonischemic. In addition, a number of patients may have an intermediate in presentation with variable clinical course. On initial presentation, it may be difficult to classify a given patient into either category, since CRVO may change with time. A number of clinical and ancillary investigative factors are taken into account for classifying CRVO, including vision at presentation, presence or absence of relative afferent pupillary defect, extent of retinal hemorrhages, cotton-wool spots, extent of retinal perfusion by fluorescein angiography, and electroretinographic changes. Nonischemic CRVO is the milder form of the disease. It may present with good vision, few retinal hemorrhages and cotton-wool spots, no relative afferent pupillary defect, and good perfusion to the retina. Nonischemic CRVO may resolve fully with good visual outcome or may progress to the ischemic type. Ischemic CRVO is the severe form of the disease. CRVO may present initially as the ischemic type, or it may progress from nonischemic. Usually, ischemic CRVO presents with severe visual loss, extensive retinal hemorrhages and cotton-wool spots, presence of relative afferent pupillary defect, poor perfusion to retina, and presence of severe electroretinographic changes. In addition, patients may end up with neovascular glaucoma and a painful blind eye.   Pathophysiology: The exact pathogenesis of the thrombotic occlusion of the central retinal vein is not known. Various local and systemic factors play a role in the pathological closure of the central retinal vein. Central retinal artery and vein share a common adventitial sheath, as they exit the optic nerve head and pass through narrow opening in the lamina cribrosa. Because of this narrow entry in the lamina cribrosa, vessels are in a tight compartment with limited space for displacement. This anatomical position predisposes formation of thrombus in the central retinal vein by various factors, including slowing of blood stream, changes in the vessel wall, and changes in the blood. Arteriosclerotic changes in the central retinal artery transforms the artery into a rigid structure and impinges upon the pliable central retinal vein, causing hemodynamic disturbances, endothelial damage, and thrombus formation. This mechanism explains the fact that there will be an associated arterial disease with CRVO. However, this association has not been proven consistently, and various authors disagree on this fact. Thrombotic occlusion of the central retinal vein can occur as a result of various pathologic insults, including compression of the vein (mechanical pressure due to structural changes in lamina cribrosa, eg, glaucomatous cupping, inflammatory swelling in optic nerve, orbital disorders); hemodynamic disturbances (associated with hyperdynamic or sluggish circulation); vessel wall changes (eg, vasculitis); and changes in blood (eg, deficiency of thrombolytic factors, increase in clotting factors). Whatever the mechanism of the occlusion of the central retinal vein, it leads to backup of blood in the retinal venous system and increased resistance to venous blood flow. This increased resistance causes stagnation of blood and ischemia of inner retinal layers. It has been postulated that ischemic damage to the retina produces angiogenesis factors, which stimulates abnormal vascularization of the posterior and anterior segment. In addition, increased blood pressure in the venous system causes break down of inner retinal barrier at the retinal capillary endothelium, leading to abnormal leakage of fluid in the retinal layers causing macular edema. Prognosis of CRVO depends upon reestablishment of patency of the venous system by recanalization, dissolution of clot, or formation of optociliary shunt vessels.   Frequency:   In the US: CRVO and branch retinal vein occlusion constitute the second most common retinal vascular disorder. The nonischemic type is more common than the ischemic type. Internationally: A large population-based study in Israel reported a 4-year incidence of retinal vein occlusion of 2.14 cases per 1000 of general population older than 40 years and 5.36 cases per 1000 of general population older than 64 years. In Australia, prevalence of vein occlusion ranges from 0.7% in patients aged 49-60 years to 4.6% in patients older than 80 years. Mortality/Morbidity: CRVO is not associated directly with increased mortality. Nonischemic CRVO may resolve completely without any complications in about 10% of cases. In about 50% of patients, vision may be 20/200 or worse. One third of patients may progress to the ischemic type, commonly in the first 6-12 months after presentation. In more than 90% of patients with ischemic CRVO, final visual acuity may be 20/200 or worse. Anterior segment neovascularization with associated neovascular glaucoma develops in more than 60% of cases. This can happen within a few weeks and up to 1-2 years afterward. It has been reported that the fellow eye may develop retinal vein occlusion in about 7% of cases within 2 years. In another report, the 4-year risk of developing second venous occlusion is 2.5% in the same eye and 11.9% in the fellow eye. Neovascular glaucoma may result in a painful blind eye. Race: CRVO does not have any particular racial preference. Sex: CRVO occurs slightly more frequently in males than in females. Age: More than 90% of CRVO occurs in patients older than 50 years, but it has been reported in all age groups.   CLINICAL Section 3 of 10    Author Information Introduction Clinical Differentials Workup Treatment Follow-up Miscellaneous Pictures Bibliography   History: Direct review of systems toward various systemic and local factors predisposing the CRVO. Significant history includes the following: Hypertension

Diabetes mellitus