NAI: never actually injured

Abstract

A female infant presented at 31 days of life following a head injury with concerning features for non-accidental injury. Examination revealed a noticeable depression in the left temporoparietal region with a concave depression of the left parietal bone on CT imaging. After careful consideration of the history and examination findings, along with standard investigations for non-accidental injury, the infant was diagnosed with faulty fetal packing (also known as congenital vault depression). The defect had almost completely resolved by follow-up at 5 months. This case represented a diagnostic conundrum not previously reported in the literature.

Background

Non-accidental injury (NAI) should always be considered when assessing injuries in young infants. There is an inverse correlation between incidence of NAI and age, with the highest rates seen in children aged <1 year (21.9 per 1000 children).¹ A missed NAI diagnosis can have devastating consequences. Conversely, an incorrect diagnosis of NAI can result in traumatic social outcomes for the patient and family.

We present the case of an infant who presented following a head injury with concerning features for NAI, including delayed presentation and previous social concerns. This case illustrates the diagnostic difficulty presented by possible NAI. It highlights the importance of maintaining a thorough, open-minded and empathetic approach, even if the initial assessment and handover appears highly suspicious for NAI.

Case presentation

A 31-day-old female infant presented to the emergency department (ED) with her mother, following a head injury. The infant was born at term via normal vaginal delivery. She had a caput succedaneum following delivery. The infant remained in the maternity hospital for the first 3 weeks of life for management of neonatal abstinence syndrome secondary to prescribed maternal methadone use. The family were known to social services prior to her delivery, and the infant’s older sibling was in foster care.

Eight days following discharge from the maternity hospital, the infant presented to the ED with her mother. From the history provided, the infant’s father had fallen asleep and accidentally allowed her to fall unwitnessed from his lap at sitting height onto a carpet floor 5 hours previously. The delayed presentation was mainly attributed to discussion between the parents regarding the need to present to hospital, given that the infant appeared well. It was reported that the infant cried immediately, subsequently tolerated a feed, and behaved normally following the incident.

On examination of the infant in the ED, there was a notable depression in the left temporoparietal area (figure 1). The infant had a normal systemic examination otherwise. CT imaging revealed a concave depression of the left parietal bone without overlying tissue swelling, intracranial haemorrhage or cortical defect (figure 2). The infant was admitted for observation. Given the incongruent mechanism and delayed presentation, investigation for possible NAI was commenced. Skeletal survey (plain film imaging of the entire skeleton) and ophthalmologic examination did not reveal any associated injuries or other signs of NAI. Screening blood tests were normal.

Figure 1.

Photograph showing a notable deformity in the left temporoparietal region (image taken on day 33 of life; 11 June 2020).

Figure 2.

CT image showing a well-defined depression in the left parietal region, without any overlying soft tissue swelling (Image taken on day 31 of life; 9 June 2020).

The two consultant paediatric radiologists who reviewed the CT brain noted that there was flattening and inward indentation of the left parietal bone. However, there was no overlying soft tissue swelling and no visible cortical breach. They proposed that this may represent the concave depression termed faulty fetal packing, as opposed to a depressed skull fracture, particularly in the absence of overlying soft tissue swelling or an associated intracranial injury.

Interestingly, the infant’s mother was insistent that the defect was new, despite being aware of the implications; and she was appropriately concerned.

Investigations

CT imaging revealed a concave depression of the left parietal bone without overlying tissue swelling, intracranial haemorrhage or cortical defect (figures 2 and 3). It was felt that this may represent the concave depression termed faulty fetal packing as opposed to a depressed skull fracture, particularly in the absence of either overlying soft tissue swelling or an associated intracranial injury. A full skeletal survey was also performed and plain film imaging of the entire skeleton found no associated injuries.

Figure 3.

Three-dimensional reconstructed image showing a well-defined depression in the left parietal region (image taken on day 31 of life; 9 June 2020).

Differential diagnosis

Following extensive review of photos and videos of the infant since delivery, it became apparent that the depression had been present from birth. It had been initially masked by a caput succedaneum and moulding. On repeat examination, it was also noted that the left pinna was slightly deformed, which was more obvious following birth.

This case presented diagnostic difficulty. The diagnosis of faulty fetal packing at 1 month of life is unusual—previous case reports have documented diagnoses shortly following delivery. The differential of intrapartum or early neonatal fracture (a so-called ‘ping-pong’ fracture) was thought to be unlikely given that the left ear pinna was also deformed (figure 4).² This was suggestive of prolonged extrinsic compression of the region in utero rather than acute intrapartum trauma (additionally, there was no history of antepartum trauma, or abnormalities noted on antenatal scans).

Figure 4.

The left pinna was noted to be deformed on examination (image taken on day 5 of life; 14 May 2020).

Outcome and follow-up

Following discussion with neurosurgery, radiology and social services, a diagnosis of faulty fetal packing was made with no further intervention warranted. The infant was discharged in the care of her parents. Outpatient follow-up at 5 months revealed almost complete resolution of the depression and now a normal appearance of the left pinna. The family continues to have input from social services as previously assigned.

Discussion

Faulty fetal packing (also known as congenital vault depression) is a congenital concave depression of the skull in a neonate. The condition has an incidence of approximately 0.01% (1 in 10 000 births).³ The more malleable fetal skull is deformed by an exaggerated or prolonged external pressure in utero,³ for example, from a fetal limb, twin, uterine fibroid or a bony prominence of the maternal pelvis.^{4 5}

Faulty fetal packing is usually an asymptomatic condition, but can occasionally be associated with underlying intracranial haemorrhage.⁶ Operative elevation of the depression, reduction of the depression by digital pressure at its edges and lifting of the depression by the application of negative pressure (eg, using an obstetric vacuum extractor) have all been used to manage the condition.^{3 4} However, in the absence of associated fracture or intracranial injury (suggestive of acute ‘ping-pong’ fracture rather than prolonged external pressure), multiple case reports have shown full and spontaneous resolution of the depression in the first 4 months of life, with the possibility of intervention if not resolved by 6 months of life.^{5 7 8}

The main differential for this congenital condition is an acquired ping-pong fracture, in which intrapartum or early neonatal trauma results in depression of the skull vault without an associated cortical break (again owing to the more malleable nature of the neonatal skull).² Differentiating these conditions can be difficult and relies heavily on history, such as instrumental/traumatic delivery or neonatal injury, and clinical examination, which may reveal bruising or other evidence of trauma.⁶

Learning points.

• This is an unusual and late presentation of a rare congenital deformity.

• This case highlights the importance of a thorough and clearly documented neonatal examination.

• Investigation of possible non-accidental injury should be thorough and include a very broad differential, even when the diagnosis appears apparent.

• Faulty fetal packing, as previous case reports have suggested, resolves with simple observation in the vast majority of cases.