Clinicians are commonly taught to check the cervical spine when patients come in with headaches. This usually involves measuring the active range of movement in the neck (ACROM). However, it’s important to take a closer look at why this is done so routinely. We need to consider what kind of information ACROM actually gives us about the cause of headaches.
ACROM: Commonly Performed, Seldom Decisive
ACROM is one of the most common physical tests used for headache assessment. It’s quick, familiar to most clinicians, and gives numbers that seem objective. But experts around the world see things differently.
A Delphi study of physiotherapists who focus on headaches found the following:
- ACROM was not rated as a top-tier assessment in cervicogenic headache (CGH)
- Its perceived usefulness dropped sharply in tension-type headache
- And even further in migraine
- Notably, a substantial number of experts didn’t assess ACROM at all in Cervicogenic Headache
So, the main question isn’t how often ACROM is used: “Why aren’t we all doing it?”
Instead, the real question is: “Why is there an expectation that ACROM can provide information it is not designed to reveal?”
Impairment Doesn’t Mean the Neck Causes the Headache
ACROM measures the extent of neck movement limitation.
It tells us:
- The neck is stiff
- The neck is sore
- Neck movement is restricted
But ACROM doesn’t tell us the following: Whether the neck is driving the head pain.
Current evidence shows:
- Many people have limited cervical movement and never get headache
- Many migraine patients have completely normal neck movement
- Movement loss does not correlate well with symptom severity or prognosis in neck pain populations
So, if neck movement is limited, we might ask, “Is the neck not working right?” but this doesn’t tell us if it’s causing the headache. It doesn’t answer this important clinical question: “Is this neck contributing to the headache?” These are two separate clinical questions.
The Problem with Specificity
The cervical spine has many segments and is mechanically complex.
ACROM:
- Reflects combined movement across many segments
- Cannot isolate upper cervical contributions
- Is influenced by pain, fear, guarding, and effort
- Has only moderate reliability, even in experienced hands
Headache of cervical origin, however, is believed to be driven primarily by upper cervical afferent input. As a result, a general movement test is often used to guess if a specific segment is causing pain. This approach doesn’t quite match up with good clinical reasoning.
Clinical Contexts in Which ACROM Is Meaningful
There is one situation where ACROM gives more than just general information. Specifically, when a patient reports that neck movement provokes their characteristic headache symptoms. In this case, the assessment is about more than just measuring movement. Here, the clinician is observing how symptoms behave.
If turning, extending, or holding the neck in certain positions reliably brings on the patient’s usual headache, then movement testing matters. But it’s important to note: This presentation is uncommon.
Large headache cohort studies demonstrate that reproduction of familiar headache with active neck movement occurs in only a small minority of patients. This makes movement-provoked headache:
- Low sensitivity
- Low specificity
So, this should only be checked if the patient’s history suggests it’s important. Furthermore, ACROM shouldn’t be used as a routine way to diagnose headache types.
Potential for ACROM to Mislead Clinicians
Clinicians like ACROM because it gives measurable data. Numbers seem objective, which can feel reassuring in practice.
But a patient may present with:
- Markedly reduced rotation
- Muscle tightness
- Thoracic stiffness
However, none of these findings actually explain why the patient has a headache. While another patient may have full movement, careful segmental upper cervical testing reproduces and then reduces their head pain. In these cases, ACROM tells us about the neck’s condition.
It does not elucidate the underlying mechanism of headache.
Focusing too much on overall movement can take attention away from more useful tests, such as:
- Segmental symptom reproduction
- Symptom modulation
- How head pain responds when the neck is loaded in certain ways. These findings are more helpful for figuring out if the neck is involved in the headache.
With all this in mind, it’s fair to ask if skipping ACROM is actually poor practice.
No, that’s not always true. It might just mean the clinician is focusing on:
- Behaviour of the head pain
- Reproduction of familiar symptoms
- Segmental provocation
- Symptom modulation
… instead of just depending on a general movement test.
ACROM can help describe what’s going on in the neck. But it rarely explains the cause of the headache.
ACROM should be seen as a background check, not the main tool for making clinical decisions.
Use ACROM to get a sense of general neck function, spot major movement avoidance, and set a baseline if there’s clear impairment.
Don’t rely on ACROM alone to diagnose if the neck is involved, tell headache types apart, or decide on treatment.
When assessing headache, the key information isn’t how much neck movement is limited. Instead, it’s how the head pain responds when specific parts of the neck are stressed. This approach gives a clearer picture of whether the neck is actually involved.
