The decision tool tells you what to do. This chapter is about why — why an injury with nothing to see can still cause a stroke, why the imaging answer flips at sixteen, why the danger runs for months, and why every route ends in safeguarding. It is meant to be read before the shift, not during it.
IFAS UK intercollegiate guideline, verbatim
Law UK statute, verbatim from legislation.gov.uk
Study named study, figures from its abstract
Observational cohort, series or audit
Teaching standard teaching, not guidance
Two guidelines, one line at sixteen. Everything below rests on the two IFAS intercollegiate guidelines — the adult and adolescent one (July 2025) and the under-16 one (July 2026). They agree on almost everything except the vessels, and there the disagreement is the point. Read the age chapters as a pair, and never carry the adult CT-angiography answer across the sixteen line.
A case to hold in mind · illustrative, not a real patient
A 28-year-old woman is brought by her partner after “a row that got physical”. He does the talking. When you get her alone she says he “grabbed me by the throat and pushed me against the wall” for what she thinks was ten or fifteen seconds; she saw flashing lights, felt she might pass out, and thinks she wet herself. That was two hours ago. Now she feels fine and wants to go — she has to collect the children. Her neck looks completely normal. Observations are normal. A colleague says: “Nothing to see, no LOC, she’s keen to go — discharge with advice.”
By the end of this chapter you should be able to name several things in that paragraph that are red flags, and two decisions in it that would be wrong. They are listed at the bottom.
The whole pathway
Why we do what we do, in one table
Every step in the decision tool, and the reason it is there.
Chapter 1
The mark that isn’t there
Why the neck can look perfectly normal after an injury that nearly killed someone.
The single most dangerous instinct in strangulation is to reason from the neck. It looks normal, so nothing happened. But pressure enough to occlude the veins, the arteries or the airway does not have to bruise the skin, and the guideline is blunt about it: “50% of victims will have no visible external injury to their neck/head as a result of the strangulation”. IFAS Modern forensic series put the figure a little lower — in a 2025 audit of 170 examined victims, 23.5% had no detectable neck injury even under forensic photography Parekh 2025 — but the direction is the same: a clean neck is common, and it is not evidence of a mild event.
So the guideline turns the usual logic around. Visible bruising or a ligature mark is a red flag if present; its absence is not a red flag removed. “A lack of visible injury MUST NOT influence decision-making around proceeding with radiological investigation.” IFAS Box A The decision tool has no checkbox for “neck looks fine”, because there is no clinical decision that should turn on it.
Where the injury actually shows, if it shows at all
When there are signs, they are often not on the front of the neck. The guideline asks you to look in places the eye skips: “Bruising from NFS may occur on the scalp, in the mouth, and/or behind the ears.” IFAS Petechial haemorrhages — pinpoint bleeds from venous congestion above the point of compression — appear on the face, in the conjunctivae, on the palate. These are among the more specific external signs, and they are easy to miss if you only look at the throat.
Why the history matters more than the examination
Because the examination is so often silent, the red flags that drive imaging are mostly symptoms, not signs: loss or near-loss of consciousness, incontinence, visual disturbance, a voice change, difficulty swallowing. Several of these are things a frightened patient will not mention unless asked directly — and they cannot be asked with the assailant in the room. That is why “see the patient alone” is not a courtesy in this guideline; it is how the red flags are found.
Chapter 2
What actually gets hurt
Four mechanisms, running on different clocks.
Strangulation is external pressure on the neck, and it damages four things, in roughly this order of speed:
- The veins. Jugular compression needs the least force. Blood backs up above the obstruction, which is what produces facial and conjunctival petechiae and the sense of the head “filling”. This can happen in seconds.
- The airway. Laryngeal and tracheal cartilage can be bruised, fractured or oedematous. The danger here is delayed: swelling can worsen over hours, which is the whole reason for the observation window.
- The arteries. Carotid and vertebral arteries can be compressed enough to cause transient cerebral hypoxia, or injured — an intimal tear that becomes a dissection, which can throw a clot and cause a stroke, sometimes days later. This is the injury CT angiography is looking for in adults.
- The brain, from hypoxia. If arterial flow or breathing is interrupted long enough, the result is hypoxic-ischaemic injury — the same process as any cardiac arrest, on a spectrum from a few dropped seconds to death.
Two things follow from this list. First, loss of consciousness is a marker of how close the event came to lethal: it means either the arteries or the airway were occluded enough to drop the brain’s supply. Second, the neck is not the only organ injured — the brain and airway are downstream of it, and they are where the delayed harm sits.
The number worth remembering about lethality
The commonly cited threshold is that only a few kilograms of pressure, applied for seconds to a couple of minutes, can be fatal — far less than most people assume, and far less than it takes to leave a mark. This is why “it was only for a few seconds and there’s no bruise” is not reassurance: the fatal range and the no-visible-injury range overlap almost completely.
Chapter 3
The vessel, and the clock that runs for months
Why 16-and-overs get a CT angiogram, why within an hour, and why “fine now” is not the end of it.
For patients 16 and over, any red flag means CT angiography of the neck and intracranial vessels, arterial phase, with bone reconstructions of the cervical spine, within one hour. IFAS Box B The target is blunt cerebrovascular injury: a carotid or vertebral tear that may be clinically silent when you see the patient and declare itself later as a stroke.
The yield is low. In an Australian two-centre cohort of 425 adult presentations, vascular injury was found in just three (0.7% of the cohort, 1.5% of the CT angiograms done), and all three were in hanging rather than manual strangulation Williamson 2022. But low is not zero, and the injury is catastrophic when missed: a German series that actively imaged suicide-attempt survivors found carotid dissection in 2 of 50 adequately imaged patients (4.0%) — while more than half the strangulation survivors had had inadequate or no imaging at all (36.4% none, 20.6% insufficient) Etgen 2023. That combination — a serious injury, uncommon but real, easy to miss clinically, and routinely under-investigated — is exactly the situation a scan-on-red-flag rule is built for.
The imaging that is not recommended
The guideline explicitly rules out the reassuring-feeling alternatives: “Ultrasound/carotid doppler ultrasound and plain X-rays are NOT RECOMMENDED for evaluation of the vascular or soft tissue structures in this setting.” IFAS And observation is not a substitute for the scan: “’Observation only’ has NO role in a suspected vascular injury and appropriate imaging is required”. IFAS
The four-week window, and the twelve-month risk
The adult pathway scans within four weeks of the event, or later if the patient is symptomatic now. The guideline is candid that the number is a judgement: “The four-week timescale for non-symptomatic patients that has been chosen is a balance of the current evidence base regarding risk of significant vascular injury, with its life changing potential, versus pragmatism”. IFAS
Crucially, “outside the window” does not mean “safe”. Patients beyond four weeks “may still be at risk of vascular problems such as carotid artery dissection due to the blunt neck trauma for up to 12 months post event.” IFAS Those with a red flag in the history “may require outpatient imaging” through a local arrangement, and “Consider antiplatelet treatment for those being referred for outpatient imaging.” The guideline gives no drug or dose — use your local protocol.
Chapter 4
Why the child is a different pathway, not a smaller adult
The one place the two guidelines deliberately disagree.
For under-16s, the answer to “which vessels do we image” is none, by CT angiography: “CT neck angiogram is not recommended in children in this context.” IFAS paed Using the adult pathway on a child is the specific error the paediatric guideline was published early to prevent — there was “concern that children and young people are being imaged unnecessarily.”
The evidence behind the change points the same way. The guideline drew on informally collected UK data on 106 consecutive children aged 17 and under who had CT neck angiography after strangulation: none had a cervical vascular injury or a cervical bony fracture. What the children who were harmed had was hypoxic brain injury. The published literature agrees — the largest series, 1929 US children after near-hanging, found blunt cerebrovascular injury in only 0.9% and cervical spine injury in 2.1%, while cerebral oedema (24.0%) was far commoner and carried the mortality; its authors concluded “a selective approach to neck imaging may be warranted.” Gorski 2024
So the paediatric pathway moves imaging toward what actually harms children after strangulation — the airway, the chest and the brain — and away from the vessels. Stridor or airway obstruction gets a CT neck with contrast (not an angiogram); dyspnoea or surgical emphysema gets a chest X-ray; a GCS below 13, new neurology, seizure or stroke gets an unenhanced CT head. IFAS paed Box B
Sixteen and seventeen are still children. They follow the adult clinical pathway — including CT angiography — but children’s safeguarding law and your local child protection procedures apply to them in full. The line at sixteen is a line about vessels, not about safeguarding.
What is deliberately absent from the paediatric red-flag list
There is no circulation category in the child list, on purpose: “In the available evidence base literature there were no specific circulation markers related to NFS to indicate imaging is required.” IFAS paed And bruising, petechiae and a history of pressure — adult imaging triggers — are not paediatric imaging triggers. In a child they remain very much safeguarding findings: “Many child victims of manual NFS will not have visible external injury to the head or neck.”
Chapter 5
The brain and the airway, after the patient looks well
The two harms that arrive late.
The six-hour airway window
Laryngotracheal injury and oedema can worsen after arrival. Both guidelines say the same thing about early presentations: consider a period of observation, because “Delayed airway difficulties are rare and likely to occur within the first 6 hours post assault, dependent on factors such as type/extent of injury etc.” IFAS A patient who is comfortable now but presented within a few hours of a significant event is not automatically dischargeable; the airway may not have declared itself yet.
Hypoxic-ischaemic brain injury, and the three-month assessment
Where consciousness was lost, the brain took a hypoxic hit, and the sequelae — cognitive, speech and language, emotional and behavioural — are frequently invisible on the day. The guideline asks that adults have a neuropsychology assessment “undertaken 3 months post the strangulation”, arranged via the GP or directly. IFAS For children the same applies with an added warning that is easy to forget: childhood brain injury can be silent and only surface years later, mistaken for a learning, attention or mental-health problem — so record “strangulation” clearly in the notes and the GP letter.
Why “GCS 15 and keen to go” is not a discharge
Three of the most important consequences of strangulation — a dissecting artery, a swelling airway, and a hypoxic brain injury — can all be present in a patient who is fully alert, comfortable and asking to leave. The decision to image, observe or refer is driven by the history of what happened, not by how well the patient looks two hours later.
Chapter 6
Why every branch ends in safeguarding
The clinical decision is often “no scan”. The safeguarding decision is never “nothing”.
In both flowcharts, every route — scanned, not scanned, and outside the window — passes through the safeguarding box before admission or discharge. There is no branch that skips it, and the reason is in the epidemiology.
Non-fatal strangulation is one of the strongest single predictors of later homicide of women by an intimate partner. In the landmark case-control study, prior non-fatal strangulation was associated with over six-fold odds of becoming an attempted homicide (OR 6.70, 95% CI 3.91–11.49) and over seven-fold odds of a completed homicide (OR 7.48, 95% CI 4.53–12.35). Glass 2008 An ED attendance for strangulation is not just an injury to treat; it is a sentinel event.
That is why the guideline gives NFS a status of its own in domestic abuse: complete the DASH risk checklist and refer to an IDVA, and refer to MARAC — the act “would warrant a MARAC referral, regardless of overall DASH score”. IFAS The strangulation earns the referral by itself; you do not wait for the checklist to cross a threshold.
6.7×odds of later attempted homicide after prior non-fatal strangulation (Glass 2008)
7.5×odds of later completed homicide (Glass 2008)
MARACwarranted by NFS itself, regardless of DASH score (IFAS)
The safeguarding box is not only about domestic abuse. It includes a suicide and self-harm assessment for everyone — “Self-harm by hanging/strangulation often indicates a very high suicide intent” — and, where there has been sexual assault, a SARC referral, emergency contraception, HIV and hepatitis B post-exposure prophylaxis and STI signposting. For children, it means a safeguarding assessment for every child and a child protection medical assessment where appropriate; sexual activity in a child under 13 “should always result in a child protection referral.” IFAS paed
Chapter 7
The law, briefly — because the notes may be read in court
What the clinician needs to know, and the line the clinician must not cross.
Since 7 June 2022, section 75A of the Serious Crime Act 2015 makes it an offence in England and Wales if a person “intentionally strangles another person”, or does any other act affecting their ability to breathe that constitutes a battery. SCA 2015 s.75A In Northern Ireland, section 28 of the Justice (Sexual Offences and Trafficking Victims) Act (NI) 2022 creates a parallel offence, committed “irrespective of whether in fact A’s act affects B’s ability to breathe or the flow of blood to B’s brain.” JSOTVA (NI) 2022 s.28 This module does not state the Scottish position.
Consent is a live issue because some strangulation is described as consensual, including during sex. In England and Wales, section 71 of the Domestic Abuse Act 2021 provides that consent is not a defence to serious harm inflicted for sexual gratification. The guideline’s instruction is therefore to stay non-judgemental while making sure the person knows about “the potential harm and the law related to ability to consent to serious harm if that occurs.” IFAS
None of this makes the ED a reporting service. The clinician’s job is to discuss reporting with the patient — considering capacity, confidentiality and best interest, under GMC confidentiality guidance — not to report on their behalf. Children and adults at risk are the exception where safeguarding duties override, and your safeguarding team is who to call. Document carefully and factually: what you write may be read in a criminal or family court.
Pitfalls
Ten ways this goes wrong
Each is a real pattern, not a hypothetical.
01Reading the normal neck as reassurance
- Why it happens
- We are trained to examine, and the examination is negative.
- Instead
- Around half have no visible injury; absence of a mark must not influence the imaging decision. IFAS Box A
02Taking the history with the partner in the room
- Why it happens
- The accompanying person is helpful, insistent, or simply there.
- Instead
- See the patient alone. Patients “are unlikely to spontaneously give a history of strangulation”, and the red flags are in that history. IFAS
03Applying the adult CT angiogram to a child
- Why it happens
- The adult guideline is familiar and the paediatric one is new.
- Instead
- No CT neck angiogram under 16. Image the airway, chest and brain by the paediatric pathway. IFAS paed Gorski 2024
04Discharging the “fine now, keen to go” patient
- Why it happens
- GCS 15, normal obs, and a patient in a hurry.
- Instead
- The dangerous injuries — dissection, airway oedema, hypoxic brain — can all coexist with looking well. Decide from the history. IFAS
05Missing loss of consciousness or incontinence
- Why it happens
- Patients do not offer them, and they are embarrassing to disclose.
- Instead
- Ask specifically. Both are red flags and both mark how close the event came to lethal.
06Ordering an ultrasound or carotid Doppler instead
- Why it happens
- It feels safer, faster and non-irradiating.
- Instead
- Ultrasound, carotid Doppler and plain X-ray are explicitly NOT recommended for the vessels here. It is CT angiography or nothing. IFAS
07Treating “outside four weeks, fine now” as cleared
- Why it happens
- No ED scan is indicated, so it feels finished.
- Instead
- Dissection risk runs up to 12 months; a red flag in the history may still need outpatient imaging, and consider antiplatelet cover. IFAS
08Doing the imaging and stopping there
- Why it happens
- The scan felt like the hard decision.
- Instead
- Every branch ends in a safeguarding screen, a suicide-risk assessment, and — in domestic abuse — DASH, IDVA and a MARAC referral. IFAS Box D
09Skipping MARAC because the DASH “wasn’t high enough”
- Why it happens
- MARAC is understood as a high-score referral.
- Instead
- NFS itself warrants a MARAC referral, “regardless of overall DASH score”. IFAS Glass 2008
10Coding it as “assault” or “neck pain”
- Why it happens
- It is quicker, and the specific word feels loaded.
- Instead
- Record “strangulation” clearly — it drives the 3-month brain-injury follow-up, the safeguarding trail, and any court process. IFAS
Red herrings
Seven findings that look reassuring and are not
None of these is wrong information. Each answers a different question from the one you are asking.
Looks reassuring
“There’s no mark on the neck.”
Around half of victims have no visible external injury; a clean neck is common and is not evidence of a mild event. Strack 2001 Parekh 2025
Looks reassuring
“She says she didn’t pass out.”
Patients often cannot be sure, and “near-loss” of consciousness is itself a red flag. Ask about vision, dizziness and the gap in memory too.
Looks reassuring
“The CT angiogram was normal.”
It excludes injury at the time of the scan. Dissection can declare itself over the following days to months — safety-net for stroke symptoms. Etgen 2023
Looks reassuring
“Vascular injury is rare — 0.7%.”
True, and it is still why we scan on red flags: the injury is uncommon, catastrophic when missed, clinically occult, and routinely under-imaged. Williamson 2022
Looks reassuring
“He only had his hands round her throat for a few seconds.”
The fatal range needs only seconds and a few kilograms of force — less than it takes to bruise. Brevity is not safety. Teaching
Looks reassuring
“The child has no bruising.”
Bruising is neither sensitive nor an imaging trigger under 16. Its absence changes nothing, and its presence is a safeguarding finding, not a scan trigger. IFAS paed
Looks reassuring
“She says it was consensual, during sex.”
That is a reason for a non-judgemental conversation about harm and the law — not a reason to close the assessment. One cannot consent to serious harm. DA Act 2021 s.71
The case, revisited
What was happening with the 28-year-old
- The partner did the talking. The history only emerged when she was seen alone — which is why the guideline requires it. (Pitfall 02)
- “Grabbed by the throat” is the history; the normal neck is not. Half have no mark, and its absence must not influence the imaging decision. (Chapter 1)
- Flashing lights, near-LOC and incontinence are three red flags. Any one of them means CT angiography within the hour for a 16-and-over patient. (Chapter 3)
- “Fine now, keen to go” is not a discharge. Dissection, airway oedema and hypoxic injury can all sit behind a normal-looking, alert patient — and she presented within the 6-hour airway window. (Chapters 3, 5)
- “Discharge with advice” skips the safeguarding box. This is domestic-abuse strangulation with children at home: DASH, IDVA, a MARAC referral regardless of score, and a documented risk assessment before she goes anywhere. (Chapter 6)
The pattern behind all of it: every reassuring feature in the vignette was true. The error is in what each was taken to mean — and in ending the assessment at the neck.