Trigger Point Injections (TPIs) are used to manage myofascial pain, which originates from muscle or fascia. The procedure targets hyper-irritable spots within skeletal muscle, often called muscle knots. TPIs are generally considered safe, but head pain is a potential side effect, though it is often mild and temporary. Understanding how an injection can lead to head pain is important for patients undergoing this procedure.
What Trigger Point Injections Are
Trigger Point Injections involve delivering a substance directly into a taut band of muscle fiber. A health professional uses a fine needle to penetrate the palpable nodule, aiming to relax the contracted muscle tissue. The injected solution typically contains a local anesthetic, such as lidocaine, which numbs the area and helps deactivate the trigger point.
Sometimes, a corticosteroid is added to the anesthetic to reduce localized inflammation. Some procedures involve dry needling, where no medication is injected at all. The primary goal is to interrupt the pain cycle initiated by the muscle knot and restore normal muscle function. TPIs are often performed in areas prone to tension and headache referral, including the trapezius muscle, the sternocleidomastoid (SCM) in the front of the neck, and the suboccipital muscles at the base of the skull.
Mechanisms That Can Cause Head Pain
The injection process can result in head pain through two pathways: local irritation and dural puncture. Localized irritation is the most common cause, where the mechanical trauma of the needle insertion causes temporary muscle soreness. This soreness, particularly in the neck and shoulder regions, can lead to referred pain, mimicking a tension headache. Muscles near the cranium, such as the upper trapezius, are known to project pain signals upward into the head and face.
Post-Dural Puncture Headache (PDPH)
The rare complication known as Post-Dural Puncture Headache (PDPH) occurs when the needle penetrates the dura mater, the tough outer membrane surrounding the brain and spinal cord. This accidental penetration creates a small hole, allowing cerebrospinal fluid (CSF) to leak out. The resulting loss of fluid volume causes a drop in pressure around the brain and spinal cord, a condition called intracranial hypotension.
When CSF pressure is reduced, the brain shifts downward upon standing or sitting. This places traction on pain-sensitive structures like the meninges and blood vessels. This downward pull is the mechanism responsible for the severe positional headache associated with a dural puncture. While TPIs are shallow procedures targeting muscle, this risk is present when injections are performed deep in the cervical or upper thoracic spine near the midline.
Identifying Severe vs. Mild Post-Injection Headaches
Patients must distinguish between a common, mild post-injection ache and the symptoms of a more severe complication. A mild, muscular headache typically has a delayed onset, often appearing hours after the procedure. This pain is generally described as dull or achy and is non-positional, meaning its intensity does not change significantly when moving upright. Mild headaches are usually responsive to over-the-counter pain relievers and often resolve within a day or two.
Characteristics of PDPH
A Post-Dural Puncture Headache (PDPH) presents with distinct and severe characteristics. The pain is typically immediate or has a rapid onset, occurring within minutes to a few days after the injection. The defining feature is its positional nature: the headache intensifies dramatically within minutes of assuming an upright posture and is relieved substantially when lying flat.
The pain from a PDPH is often severe and throbbing, frequently located in the front or back of the head. Secondary symptoms may include nausea, dizziness, neck stiffness, and changes to hearing or vision, such as tinnitus. Recognizing the positional nature of the pain is the primary method for identifying a PDPH.
When to Seek Medical Attention
For mild headaches following a Trigger Point Injection, patients can manage discomfort conservatively. Resting, maintaining adequate hydration, and using mild, non-prescription analgesics help alleviate muscle soreness and referred pain. These mild symptoms should generally improve within 48 to 72 hours.
Contact the treating physician immediately if the headache is severe and exhibits the positional characteristics of a Post-Dural Puncture Headache. Any headache that worsens significantly when sitting or standing and improves when lying flat requires urgent medical evaluation.
Several “red flag” symptoms warrant immediate emergency attention, as they suggest a potentially more serious underlying issue. These warning signs include the onset of a fever, severe neck stiffness, or any neurological changes such as confusion, weakness, or double vision. A headache that does not improve even when lying down should also be rapidly assessed to rule out other complications.