C. Adamsbaum^a,b
aFaculté de Médecine
Université Paris Sud
Le Kremlin Bicêtre, France
^bAssistance Publique-Hôpitaux de Paris
Centre hospitalier universitaire Bicêtre
Service d’Imagerie Pédiatrique
Le Kremlin Bicêtre, France

C. Rey-Salmon^c
cAssistance Publique-Hôpitaux de Paris
Centre hospitalier universitaire Hôtel Dieu
Unité Médico-Judiciaire
Paris, France

The article by Wittschieber et al¹ offers very interesting insights into subdural hygromas (SDHys) in the particular context of abusive head trauma (AHT).

We definitely agree that any pericerebral subdural collections—that is, hygromas or chronic subdural hematomas (true evolution within a few weeks of a subdural hematoma)—should prompt pediatricians to strongly consider AHT if all other classic etiologies have been ruled out.

We would, however, like to comment on the issue of dating the causal episode in cases of SDHy. The authors offered 2 possible concepts to explain SDHy formation: delayed formation as an intermediate stage of a subdural hematoma and rapid formation from a tear in the arachnoid membrane. The term “acute SDHy” is suggested for the latter case, which usually consists of both CSF and blood (giving it its so-called “mixed-attenuation” appearance). As a result, the mixed-attenuation pattern cannot be used to date the causal event. We agree with this completely.

However, we disagree with the idea that in the context of violent acceleration-deceleration, an acute SDHy can occur without any hemorrhagic component and, therefore, present as a homogeneous hypoattenuated pattern such as that shown in Fig 3 of the article. In fact, consideration of the head circumference is of major importance. Figure 3 illustrates the case of an infant presenting with a sudden increase in head circumference—from the 50th to 90th percentile—in 1 month. We could hypothesize that the sudden increase in head circumference suggests the presence of a previous subdural hematoma, 1 month earlier, due to previous shaking. The small, hyperintense, subacute subdural hematoma in the posterior fossa, along with retinal hemorrhages, may indicate more recent bleeding due to a more recent shaking episode. Such an “age-different” pattern is important to recognize, given that shakings are often repeated.² In our opinion, the head circumference is a key sign—when available—that a subdural collection may be related to a previous subdural hematoma and therefore to a previous episode of shaking. Therefore, we disagree with the authors’ conclusion that “the SDHy in this well-documented case can be regarded as a result of acute injury,” and we believe that this is a case of repeated shaking.

Considering all previous clinical signs and symptoms, including head circumference, is crucially important when using imaging features to assess the “age-different” patterns of subdural collections.³ This is not only a legal issue in the courts but also a key diagnostic sign for AHT.

References

1. Wittschieber D, Karger B, Niederstadt T, et al. Subdural hygromas in abusive head trauma: pathogenesis, diagnosis, and forensic implications. AJNR Am J Neuroradiol 2015;36:432–39 » Abstract/FREE Full Text
2. Adamsbaum C, Grabar S, Méjean N, et al. Abusive head trauma (AHT): judicial admissions highlight violent and repetitive shaking. Pediatrics 2010;126:546–55 » Abstract/FREE Full Text
3. Adamsbaum C, Morel B, Ducot B, et al. Dating the abusive head trauma episode and perpetrator statements: key points for imaging. Pediatr Radiol 2014;44(suppl 4):578–88 » CrossRef

Reply

D. Wittschiebera and B. Karger^a
aDepartment of Forensic Medicine
University Hospital Münster
Münster, Germany

T. Niederstadt^b
bDepartment of Clinical Radiology
University Hospital Münster
Münster, Germany

H. Pfeiffer^c
cDepartment of Forensic Medicine
University Hospital Münster
Münster, Germany

M.L. Hahnemann^d
dDepartment of Diagnostic and Interventional Radiology and Neuroradiology
University Hospital Essen
Essen, Germany

With great interest we read the letter by Drs Adamsbaum and Rey-Salmon concerning our article “Subdural Hygromas in Abusive Head Trauma: Pathogenesis, Diagnosis, and Forensic Implications.”¹ We are very grateful for their interest in our work.

Because during neuroimaging we frequently observe the concomitant occurrence of hyper- and hypodense subdural collections (mixed-density pattern), in both the same location and at least 2 different locations, we were interested in the possible pathophysiologic mechanisms that underlie the formation of the hypodense component (ie, subdural hygromas [SDHys]). The currently available literature reveals the presence of the 2 major hypotheses that we outlined in our review article (delayed and rapid formation of SDHys).¹ Of course, we are aware that the pathophysiology of SDHy formation is still an ongoing research process, and it seems very likely that multiple mechanisms exist and coexist.

Dating the incident by estimating the age or stage of a subdural collection is an even more controversial issue and has a high potential for confusion, especially the question of how many shaking events might have occurred. Repeated shaking, of course, may definitely cause corresponding injuries such as seen in the “age-different” pattern described by Adamsbaum et al.^2,3

In regard to the case example shown in Fig 3 of our article¹ however, we can exclude, due to the child’s medical history, a previous subdural hematoma (SDH) being present 4 weeks earlier. The infant had been clinically examined at relatively short intervals since birth, and the clinical records did not reveal any abnormalities 1 month before the MR imaging, in either cranial sonography or clinically. Membranes organizing the subdural collection and supporting the assumption of an earlier formation of the SDHy⁴ were not discernable in the MR imaging either. We totally agree with the opinion that in the context of violent acceleration-deceleration, the occurrence of an acute SDHy without any hemorrhagic component or sediment could be considered unusual. We hypothesize that in addition to a tear in the arachnoid membrane, a hemorrhagic component might not be missing but is possibly only a minor part of the subdural collection, suggesting only a minor vascular injury in the frontoparietal region and a rapid influx of a significant amount of CSF and/or CSF-like liquid. This could explain not only the sudden increase in head circumference from the 50th to the 97th percentile but also the slightly higher signal intensity of the SDHy in Fig 3 compared with the “pure” CSF within the subarachnoid space. The formation of an acute SDHy within 20 hours in a different location than the acute SDH has also been directly observed during serial neuroimaging.⁵ In general, subdural hypodensities (ie, SDHys) have been shown to appear much sooner than the 1–4 weeks accepted previously.^5⇓–7

These data exhort us to be careful with the age estimations of subdural collections, not only with regard to mixed densities in a single location (eg, due to serum separation and sedimentation of erythrocytes^4,7) but also in different locations. Accordingly, we think that the subdural pathologies of the infant presented in Fig 3 do not necessarily indicate an additional abusive head trauma (AHT) that occurred 4 weeks earlier. Instead, the clinical findings, serial neuroimaging, and the available literature suggest more recent trauma including, of course, the possibility of repeated shaking within a short interval. Hence, we still believe that the SDHy in this case “can be regarded as a result of acute injury.”¹

We definitely agree with Drs Adamsbaum and Rey-Salmon that recognizing early clinical signs and symptoms of AHT is crucially important. In this context, we would also like to stress the vital importance of close and efficient cooperation among all medical disciplines involved in AHT cases (ie, pediatrics, ophthalmology, forensic medicine, and radiology in particular). Only a fast and reliable diagnosis facilitates legal certainty and appropriate therapy for infants with AHT.

References

1. Wittschieber D, Karger B, Niederstadt T, et al. Subdural hygromas in abusive head trauma: pathogenesis, diagnosis, and forensic implications. AJNR Am J Neuroradiol 2015;36:432–39 » Abstract/FREE Full Text
2. Adamsbaum C, Grabar S, Méjean N, et al. Abusive head trauma (AHT): judicial admissions highlight violent and repetitive shaking. Pediatrics 2010;126:546–55 » Abstract/FREE Full Text
3. Adamsbaum C, Morel B, Ducot B, et al. Dating the abusive head trauma episode and perpetrators statement: key points for imaging. Pediatr Radiol 2014;44(suppl 4):S578–88 » CrossRef » Medline
4. Hedlund GL. Subdural hemorrhage in abusive head trauma: imaging challenges and controversies. J Am Osteopath Coll Radiol 2012;1:23–30
5. Dias MS, Backstrom J, Falk M, et al. Serial radiography in the infant shaken impact syndrome. Pediatr Neurosurg 1998;29:77–85 » CrossRef » Medline
6. Bradford R, Choudhary AK, Dias MS. Serial neuroimaging in infants with abusive head trauma: timing abusive injuries. J Neurosurg Pediatrics 2013;12:110–19 » CrossRef
7. Vezina G. Assessment of the nature and age of subdural collections in nonaccidental head injury with CT and MRI. Pediatr Radiol 2009;39:586–90 » CrossRef » Medline