Keran Henderson Innocent website
June 26th, 2011Hi,
Found this on another site, just in case you missed it…
Thursday, 2 June 2011
Forensic Science International Axonal Injury are NOT diagnostic of Trauma
A Local Authority v S Justice Eleanor King relied on Dr Al Sarraj and criticised Drs Cohen and Squier - looks like she was wrong and relied on a doctor who really did have a polarised unscientific view! X Y and Z coming on this one!! Oh and looks like Keran Henderson has just been cleared doesn’t it! Who needs the Judges or lawyers any more eh! Just leave it to the scientists, the single journalist and the campaigner!
Triad + going out of that window!
Spinal nerve root β-APP staining in infants is not a reliable indicator of trauma.
Squier Wa FRCP FRCPath (Corresponding author)
aDepartment of Neuropathology
West Wing, John Radcliffe Hospital,
Oxford OX23 9DU
Email: waney.squier@clneuro.ox.ac.uk
Tel 01865 234932 Fax 01865 2321157
Scheimberg I b
bDepartment of Cellular Pathology
Pathology & Pharmacy Building
Barts and the London NHS Trust
London E1 2ES
Smith, C MD FRCPath
Academic Department of Neuropathology, University of Edinburgh, Wilkie Building, Teviot Place, Edinburgh, EH8 9AG, UK
Ethics
This study has been undertaken with approval of the Local Research Ethics Committee (10/H0604/83) and the local NHS research governance regulations (Ref 6321).
Contributors
Dr Squier was responsible for the initial observations and planning the study. Dr Smith reviewed all the pathology and contributed to the preparation of the manuscript. Dr Scheimberg contributed to the preparation of the manuscript. All of the authors have approved the final manuscript.
Abstract
This preliminary communication describes seven babies with b- amyloid precursor protein (βAPP) positive axonal swellings in nerve root at multiple levels of the spinal cord. All seven babies died of natural causes. Two died in utero providing evidence for nerve root injury in the absence of trauma, two died within one day of birth and the possibility of birth related injury has to be considered. Three babies were over one month of age and had no history or pathological evidence of trauma.
These findings show that if axonal injury is carefully sought in every infant death, not just in babies where trauma is suspected, it will be found in a proportion of babies dying from natural diseases. While spinal nerve root axonal injury in infants may suggest trauma, it is not, in itself, diagnostic of trauma.
Keywords: spinal nerve root, axonal injury, infant trauma, βAPP
Introduction
Axons are the processes arising from neuronal cell bodies and are involved in a constant flow of proteins, including βAPP, between the neuronal cell body and its peripheral synapses. Disruption of axonal flow is an indication of some form of axonal injury which may be metabolic, including ischaemic, or traumatic. Immunocytochemistry for b-APP is the most widely used marker of axonal injury in routine forensic neuropathology. The patterns demonstrated in adults using this marker may enable a diagnosis of diffuse traumatic axonal injury (TAI) (1), but there have been few studies to assess the patterns and incidence of TAI in the paediatric population. Indeed, studies of cases labelled as “non-accidental injury” have demonstrated that diffuse TAI is rare in infants, but they may exhibit focal brainstem axonal injury (2-4).
We are unaware of any detailed systematic study of nerve root injury at all levels of the spinal cord in adults or infants, whether due to trauma or any other cause. Two studies have referred to nerve root damage of the cervical spinal cord; Geddes (3) and Shannon (5) described damage to the cervical spinal cord and dorsal nerve roots in babies thought to have suffered non-accidental injury (NAI). Oehmichen (4) examined the cervical spinal cord in 5 cases of NAI and identified focal axonal injury in two.
There are rare mentions of nerve root injury in the absence of trauma; Shannon refers to axonal swelling in a single nerve root of a baby who drowned (5) and Dolinak noted axonal injury of the dorsal root entry zone in cases without any traumatic injury (6).
This preliminary communication is intended raise awareness of this issue by bringing attention to our observation of βAPP positive axonal swellings in spinal nerve roots in a group of neonates and in infants with no history of trauma. This is a matter of concern as it has been suggested that selective spinal nerve root expression of ß-APP is indicative of trauma (7).
Our observations highlight the need for detailed systematic studies of spinal cord pathology in the infant.
Material and Methods
During the course of routine diagnostic practice, seven babies were identified with nerve root swellings expressing ßAPP at multiple spinal levels. As this is suggested to be a diagnostic feature of trauma, these cases were reviewed. Case details are set out in table 1.
Brains and spinal cords were fixed for between 10 days and 3 weeks in 10-20% formalin. Sections were stained for ßAPP (Invitrogen) diluted 1/10,000 after endogenous peroxidase blockade and antigen retrieval by autoclaving and formic acid treatment. Stain was developed with Envision kit (Dako) and counterstained with haematoxylin.
Results
In each of our cases clusters of axonal swellings expressing ΒAPP were seen in nerve roots at one or more levels of the spinal cord. ΒAPP positive swellings were identified in dorsal and ventral nerve roots and in nerve roots lateral to the cord as they united to cross the dura. (Figure 1).
Swellings were seen in axons both within the dural sheath and in extradural nerve roots, sometimes also in the dorsal root ganglia (Figure 2). In one case the level and position of axonal swellings was not noted.
We saw well defined axonal swellings in an eighth case, a young child who drowned, but we do not have consent to use this case for research.
The majority of nerve roots did not express βAPP (Figure 1d).
βAPP was frequently expressed in neuronal cell bodies of the spinal cord and was particularly strong in those of the dorsal root ganglia.
In some cases we noted congestion of nerve roots as they cross the dura, sometimes associated with extradural bleeding (Figure 3).
Discussion
We have identified spinal nerve root axonal swellings in seven infants with no clinical or pathological evidence of trauma.
Mechanical trauma and shearing may both cause interruption of axonal transport which results in swellings, beading and varicosities. Axonal swellings strongly express a number of immunohistochemical markers including b- amyloid precursor protein (b-APP), neurofilaments, and NSE; ßAPP is a widely used as a sensitive and specific marker of axonal injury (8). However, similar axonal swellings are seen in a variety of other conditions, including hypoxia-ischaemia and metabolic damage such as hypoglycaemia and carbon monoxide poisoning (1). In routine practice the commonest differential diagnosis lies between diffuse traumatic axonal injury and axonal injury secondary to global ischaemic injury.
Our results may be considered in two groups: babies who died before or shortly after birth and babies who died more than one month after birth.
Babies dying in the perinatal period
Two babies (cases 1 and 2) were stillborn and, as development of axonal swellings is a vital process, the axonal swellings in these babies must have been acquired prior to birth. These cases provide convincing evidence that birth trauma was not a cause of their axonal damage and generalised hypoxic-ischaemic injury is a likely cause.
Two babies (cases 3 and 4) died within one day of birth, one by vaginal delivery, the other by Caesarian section. In these babies the possibility of nerve root trauma during delivery becomes relevant.
The spinal nerve roots within the spinal canal are relatively protected from direct mechanical impact, but they may be subject to stretching and tearing if the spine is flexed abnormally. Cadaveric and animal imaging studies have shown that flexion of the spine causes stretching and medial displacement of the nerve roots of the cauda equina(9). In adult cadavers flexion of the trunk caused displacement of the cord of up to 1.8 cm, the maximum displacement being between cord levels C8 to T5 (10). These findings suggest that hyperflexion or extension of the head on the neck could be capable of causing nerve root traction at multiple spinal cord levels. Geddes (2) suggested that brainstem and cervical spinal cord damage may result from hyperflexion or hyperextension of the head on the neck, a mechanism proposed in shaking injury.
Cervical spinal cord damage has been described after both vaginal and caesarean deliveries (11). Brachial plexus nerve root injury usually occurs in malpresentations and after instrumental delivery and tends to be associated with shoulder dystocia, large babies and a long second stage (12). Some cases are due to an insult in utero and brachial palsy has been clearly documented in cases with no traction (13).
Case 3 was a vaginal delivery who was floppy at birth and survived 12 hours. There was no evidence of trauma. It may be suggested that a floppy baby may be more likely to succumb to the forces of delivery which would be transmitted to the neck if muscle tone is reduced. This hypothesis has not been tested.
Case 4 was a caesarean section with a forceps extraction associated with parietal skull fracture, which is clear evidence of trauma. Skull fractures represent 2.3% of birth injuries (14), they are more common in instrumental deliveries but can also be seen in spontaneous vaginal deliveries or caesarean sections (15). They may be caused by compression from forceps blades or from the skull pushing against the maternal pelvis (16). In case 4 trauma was probably due to compressive forces from forceps application and does not imply transmission of excessive hyperextension or hyperflexion forces to the neck or spine, but this cannot be excluded.
Babies dying after the perinatal period
None of the babies dying after 1 month after birth (cases 5-7) had either a clinical history or pathological evidence of trauma. Causes of death were apnoea of unknown cause, myocardial infarction following heart surgery and spontaneous rupture of an intracranial aneurysm.
Axonal swellings may develop within 35 minutes of injury (17) and in the adult central nervous system occasional swellings have been identified up to 3 years after trauma (18;19). We do not know if these timings apply to infants as no study addresses this in this age group. As all of our cases were under 3 years of age we cannot be certain that the axonal swellings are not the result of birth-related trauma.
A common factor in our older cases (5,6,7) was extensive, severe brain swelling. All had a clinical history of collapse and hypoxia and histological features of acute hypoxic-ischaemic injury (HII). The focal and patchy pattern of axonal injury we identified, with marked asymmetry between or within fascicles is characteristic of the pattern recognised in adult ischaemic peripheral nerve damage (20) and suggests this to be the likely cause.
Severe brain swelling may itself cause cervical nerve root injury by displacement and compression of the cervical spinal cord. Further distortion of the cervical cord and traction on cervical nerve roots may be seen if there is displacement of the cerebellar tonsils or masses of ectopic cerebellar tissue into the spinal canal, which is not uncommon in infants. None of our cases had brain swelling of this degree and in none of this series was there cerebellar displacement into the spinal canal.
Nerve root appearances
Axonal swellings were identified at multiple cord levels in most cases and were most common in the lateral roots where nerve bundles united to pass through the dural sleeve. Ventral nerve root swellings appeared to be more frequent than dorsal but no formal assessment was made in this preliminary study. Axonal βAPP expression was seen within the dorsal root ganglia in one case. In another case ganglion cells were seen among the intradural nerve roots and could be mistaken for axonal swelling on a cursory examination (Figure 2b).
In some nerve roots ßAPP expression was subtle, not associated with marked swelling and seen in only a few fibres. While unlikely to have been diagnosed as trauma by most pathologists, these mild appearances have been noted because confirmation bias may lower the threshold for diagnosis of axonal injury when faced with a case where trauma is suspected. This underlines the need for an objective analysis of spinal nerve root pathology in infants dying from all causes.
Nerve root congestion and haemorrhage
Some cases showed extensive congestion of the nerve roots as they cross the dura and in the adjacent epidural region. These regions have an extensive vascular plexus involved in spinal fluid absorption (21). Congestion and bleeding from the extensive vascular plexuses around spinal nerve roots may be related to changes in intracranial and abdominal pressure (22;23), is frequently seen in HII and is not a reliable indication of trauma.
Conclusion
It has been our experience that, if spinal nerve roots are routinely and carefully examined in babies dying from natural diseases, axonal pathology may be seen at all levels of the spinal cord in babies dying shortly after birth and in infants with no history or evidence of trauma. b-APP immunostaining in nerve roots is not, of itself, diagnostic of traumatic axonal injury.
Our evolving understanding of the distribution and significance of axonal injury in the brain has relied on detailed studies of b-APP immunostaining; similar studies are required to fully understand the pathology in spinal cord and nerve roots. The pathologist making a diagnosis based on this method must be aware that the expression of b-APP is only an indication of axonal dysfunction and is not diagnostic of mechanical trauma, such as axonal transaction, or irreversible damage.
This study is not systematic or exhaustive but serves to warn that caution is indicated in the interpretation of spinal nerve root injury in infants. Axonal swellings per se, even at multiple cord levels, are not diagnostic of trauma.
Acknowledgements
We are grateful to all those parents who have given us consent to study the brains of their babies. Cases were sent for routine clinical diagnosis by Drs Colene Bowker, Stephen Gould, Irene Scheimberg and Liina Kiho. We thank Dr Steve Gould for his helpful commentary of the manuscript. We acknowledge the skill and dedication of the laboratory staff at the Department of Neuropathology at the John Radcliffe Hospital Oxford who carried out technical work and stained the sections.
|
Case Number |
Age |
Time since collapse |
Cause of Death |
Pathology |
D/V/L |
Level |
|
1 |
35.40 |
- |
Intracranial haemorrhage seen in utero. CS, stillborn. |
Maceration Recent IVH and global HII. Old PVL Recent intravascular thrombosis. |
D,V,L |
T,S |
|
2 |
37.40 |
Days-weeks |
Polyhydramnios, Brain noted to be abnormal in utero. CS. |
Old HII and widespread necrosis. Macerated baby, no evidence of trauma. |
L |
T |
|
3 |
38.40 |
1d |
Polyhydramnios. Floppy at birth. Seizures, possible metabolic disease |
Recent global intrauterine HII. No evidence of trauma . No SDH. |
D,V,L |
T, L, S |
|
4 |
40/40 |
12h |
Emergency CS Birth asphyxia and birth trauma |
Right parietal skull fracture, subpial and subarachnoid haemorrhage. HII |
D,V, L |
T, L, S |
|
5 |
1/12 |
3h |
Multiple apnoeic episodes. Apnoea, collapse, resuscitated for 3h |
Acute brain swelling and HII. Hippocampal microglial proliferation. No evidence of trauma no SAH or SDH |
D,V |
C , S |
|
6 |
3 m |
3d |
In hospital collapse following repair of CHD. Myocardial infarction |
Recent global HII. No SDH |
V |
C, IIIn |
|
7 |
9m |
2d |
Rupture of vein of Galen aneurysm |
Global HII. Acute white matter necrosis (PVL) |
Not recorded |
Not recorded |
Figure 1
1a: (Case 4) Section of lumbar spinal cord stained with βAPP. Even at low power nerve roots crossing the dura (d) can be seen to express this protein. There is diffuse staining of some white matter tracts and nerve cell bodies within the cord (Original magnification x 4).
1b: (Case 4) Higher power image of nerve roots crossing the dura in Figure 1a. Diffuse expression of βAPP is seen in many roots as well as groups of well defined swellings (Original magnification x 20).
1c: (Case 1) Sacral cord, patchy expression of βAPP in small groups of axons within a fascicle (Original magnification x 20).
1d: (Case 1) Thoracic cord, nerve roots are negative, but swollen axons expressing βAPP are seen at the periphery of the adjacent spinal cord (SC) (Original magnification x 20).
Figure 2
2a: (Case 2) Dorsal root ganglion at thoracic level. Ganglion cells are strongly positive as are a number of axons within the ganglion (Original magnification x 40).
2b: (Case 3) Sacral cord; two ganglion cells among nerve roots beneath the dura. Note strong positivity in ganglion cells and a few swollen axons in adjacent nerve roots (Original magnification x 20).
Figure 3
(Case 1) H&E stained section of thoracic spinal cord showing marked congestion and fresh subarachnoid and subdural (SD) bleeding and intradural congestion. Note the congestion of the nerve roots as they unite to cross the dura (arrows). This region is responsible for CSF resorption.
Reference List
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84. Dr. Al-Sarraj also examined the spinal cord. The axon is a nerve fibre which connects other nerve cells. They are generally in bundles. Protein comes down the fibres. One of the proteins is ßAPP i.e. Beta-Amyloid Precursor Protein. If the axon is damaged for any reason, normal transmission will be interrupted and beads or swelling may be found along it. Such observations can be used as an indicator of damage, if deposition is seen in the spinal nerve roots it raises the possibility of traumatic root damage.
85. The identification of such damage does not in itself tell a neuropathologist whether the cause of the damage is due to ischemia or trauma. Multiple deposits were seen in the anterior horn cells (this is grey matter with nerve cells within the spinal cord itself) that is complimentary to a finding of ischemia. To Dr. Al-Sarraj of particular significance, however, is the ßAPP stain deposition seen in the spinal nerve roots which are found outside the actual spinal column.
86. At the top of the spinal cord, at the cervical segment, Dr. Al-Sarraj found a heavy deposition. At the thoracic segment there was a focal deposit in a few posterior spinal root nerves and in the lumbar region very occasional small deposits in one or two posterior spinal roots.
87. Due to the fact that these depositions in the spinal nerve roots are mainly in the posterior aspect and focal, rather than throughout the spinal cord, this raised the possibility to Dr. Al-Sarraj of the possibility of traumatic axonal damage. Although ischemia (which was seen throughout the spinal cord), could not be completely excluded as the cause of an axonal injury, it was, he said, also possible that it was the consequence of the movement of the spinal cord and stretching of the nerve roots in shaking. In other words, a hyper-flexion, hyper-extension injury.
88. ßAPP examination in the cranial nerve roots of the brain was carried out. This is done routinely. Although there is no peer reviewed literature as yet published, this is an area of research in which Dr. Al-Sarraj’s department is engaged. Damage in that location would tend to favour ischemia and in Z’s case there was no evidence of axonal damage in the cranial nerve roots. When the cranial nerves are not involved and only local and posterior spinal nerves, whilst you cannot totally exclude ischemia as the cause, it is more likely, Dr. Al-Sarraj said, to be due to trauma.
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