While most stiff necks result from minor muscle strains or ligament sprains, a stiff neck caused by meningitis is a vastly different process that stems from a potentially life-threatening infection. This page examines why neck stiffness is present in some cases of meningitis.
The Anatomy and Function of the Meninges
The meninges are the protective layers covering the brain and spinal cord. The cranial meninges cover the brain and cushion it from the skull; the spinal meninges cover the spinal cord and protect it from direct contact with the cervical spine (neck) and thoracic spine (chest).
In addition to protecting the brain and spinal cord, the meninges also help direct the flow of blood to the skull and brain, as well as transport cerebrospinal fluid. Cerebrospinal fluid is formed in the brain and flows freely through the cranial meninges and into the spinal meninges.
The three layers of the meninges include:
- Dura mater. The outermost layer is the toughest and comprised of dense fibrous tissue, which provides the most protection. The dura mater is the only layer of the meninges that is sensitive to pain.
- Arachnoid mater. The middle layer is filled with elastic tissues and collagen in a spider web-like structure, which is how this layer gets its name. The cerebrospinal fluid runs beneath the arachnoid mater in the subarachnoid space and above the pia mater.
- Pia mater. The innermost layer attaches to and closely lines the spinal cord and brain, unlike the looser-fitting arachnoid mater and dura mater on the outside. The pia mater is the thinnest and most delicate of the three meningeal layers.
Most commonly in meningitis, the cerebrospinal fluid and its surrounding meninges—the arachnoid mater and pia mater—are infected and inflamed. While the dura mater may have little to no inflammation, its nerve fibers may become activated and contribute to neck pain and nuchal rigidity.1
Meninges and Neck Stiffness
To understand why meningitis can cause neck stiffness, it helps to think about how the meninges cover the brain and spinal cord, which runs through the neck and torso region but stops shy of the lower back. Of these areas where the meninges run, only the neck is highly mobile. (The thoracic spine is mostly stabilized by the ribs to protect internal organs.) If the meninges become inflamed and painful with movement, the reduction in movement will be most noticeable in the neck.
Clinical Tests for Meningeal Inflammation May Not Help
If the patient history raises suspicions for meningitis—such as neck stiffness, severe headache, and/or living in close quarters where infections easily spread—clinical tests might be performed in the doctor’s office to help gauge whether the meninges are potentially inflamed. These tests could include:
- Nuchal rigidity. When the neck cannot flex forward all the way, nuchal rigidity (neck stiffness) is present. This could possibly be due to neck muscles stiffening to avoid painful movements of the meninges within the cervical spine.
- Brudzinski’s sign. With the patient in a supine position (lying on the back), the head is gently lifted upward. If the hips and knees flex as a result, Brudzinski’s sign is positive. In theory, moving the neck upward causes the inflamed meninges surrounding the spinal cord to stretch, and the hips and knees reflexively move upward to compensate and reduce the tension.
- Kernig’s sign. With the patient in a supine position, the knee is lifted and then the leg is gradually extended. If pain results and the movement to straighten the leg is resisted, Kernig’s sign is considered positive.
- Jolt accentuation. A patient with headache and fever turns the head side to side two or three times per second. If the headache worsens, the test is considered positive. Jolt accentuation is typically done for someone reporting headache but not neck stiffness.
Multiple studies have found these clinical tests to be of little to no value in diagnosing meningitis, but they are still widely used today.2,3 One study, however, found that positive results for Brudzinski’s sign, Kernig’s sign, and jolt acceleration together with fever and headache do indicate a greater likelihood for meningitis to be present.3 It is also possible that the usefulness of these clinical tests could be dependent on the specific type of organism causing meningitis.
Regardless of the results, meningitis cannot be ruled in or out based on these clinical tests alone. Diagnostic lab results from the spinal tap are needed to make an official meningitis diagnosis.