Why Can't I Feel Hot or Cold on My Arms and Shoulders?

If you have a Chiari malformation and are losing the ability to feel temperature (or pain) across your arms, shoulders, and upper back, this is a classic, suggestive sign of a condition called syringomyelia ^[1]. Syringomyelia occurs when a fluid-filled cavity (a syrinx) forms inside your spinal cord. As this cavity expands, it can press on the specific nerve pathways that carry hot and cold signals from your upper body to your brain, which may create a “cape-like” pattern of numbness ^[2]. While this pattern is highly suspicious for a syrinx, it is not an absolute diagnosis—other nerve, spinal, or brain issues can cause similar symptoms, so a clinical exam and imaging are required.

The Plumbing Problem: How a Syrinx Forms

Your brain and spinal cord are bathed in cerebrospinal fluid (CSF). Normally, this fluid pulses freely back and forth between your brain and spine with every heartbeat.

In a Chiari malformation, the lower part of the brain (the cerebellar tonsils) rests abnormally low, pushing into the opening at the base of your skull ^[3]. This physical crowding acts like a bottleneck that alters the normal dynamics of CSF flow ^[4]. The exact mechanism is still being studied, but it is believed that these abnormal pressure waves can drive spinal fluid into the tissue of the spinal cord ^[5]. Over time, this fluid can pool to form a syrinx within the cord itself. Not everyone with a Chiari malformation develops a blocked CSF pathway or a syrinx, but when it happens, it can cause physical pressure on the nerves.

Why You Lose Temperature Sensation First

To understand why you lose the ability to feel hot and cold in your arms, it helps to look at how nerves are wired inside the spinal cord.

Nerve signals for different senses travel up the spinal cord in different “lanes.” The fibers responsible for carrying pain and temperature signals cross over right in the very center of the spinal cord, in a specific region called the anterior white commissure ^[6].

Because a syrinx typically forms near the center of the spinal cord, it injures these crossing temperature and pain fibers first ^[6][1]. Meanwhile, the nerve fibers responsible for fine touch, vibration, and knowing where your arms are in space (proprioception) travel along the posterior (back) columns of the spinal cord. Because they are further from the center, these pathways often remain unharmed in the early stages.

Doctors call this dissociated sensory loss ^[1]. This means your senses are split: you might easily feel the light brush of a cotton ball or a vibrating tuning fork on your arm, but be completely unable to feel a hot cup of coffee or a freezing ice cube ^[1].

The “Cape-Like” Pattern

Chiari-related syrinxes most commonly form in the cervical (neck) region of the spinal cord, affecting the nerves that supply your arms, shoulders, and upper chest. When numbness develops in these areas, it often drapes over the upper body like a shawl, which is why it is called a “cape-like” distribution ^[1][2]. However, a syrinx does not always expand perfectly symmetrically, so the numbness might be patchy, uneven, or affect one side more than the other.

Symptoms can vary widely. If the syrinx continues to involve more of the spinal cord over time, it can eventually reach other nerve tracts, potentially leading to muscle weakness, wasting in the hands, or problems with walking and balance ^[1]. However, progression is not inevitable, and many people do not develop all of these problems. The goal of medical follow-up is to detect any meaningful change early.

How This Fits With EDS and Dysautonomia

You are reading this as part of a broader guide on Chiari, Ehlers-Danlos syndrome (EDS), and dysautonomia. While these conditions are frequently associated with one another, they affect the body in distinct ways:

• Ehlers-Danlos Syndrome (EDS): EDS involves weak connective tissues. Some patients with EDS develop craniocervical instability, which is excessive movement or looseness at the skull base and neck ^[7]. This instability may be associated with Chiari crowding, though EDS does not automatically cause or worsen Chiari in everyone ^[8][9].
• Dysautonomia: Conditions like Postural Orthostatic Tachycardia Syndrome (POTS) involve the autonomic nervous system, which controls automatic bodily functions like heart rate and blood pressure ^[10]. Symptoms include light-headedness or racing heart upon standing.
• Syringomyelia: The cape-like loss of temperature and pain sensation is a direct physical nerve injury caused by a structural syrinx. It is a separate issue from the systemic symptoms of dysautonomia ^[1].

It is helpful to mention any EDS or dysautonomia diagnoses to your care team, as these conditions may require special attention during anesthesia, positioning, or recovery planning if a procedure is ever considered.

Protecting Yourself: Burn Safety

If you cannot feel hot or cold on your arms and hands, you are at a high risk for accidental burns or frostbite. Practical safety steps include:

• Checking bath or shower water temperature with a reliable thermometer or an unaffected part of your body (like your foot or leg) before stepping in.
• Avoiding the use of heating pads or hot water bottles on any areas where you have numb skin.
• Wearing protective gloves and using visual checks when cooking, handling hot objects, or spending time in freezing weather.
• Inspecting your arms and hands daily for cuts, blisters, or burns you may not have felt happening.

When to Seek Care & What Happens Next

If you are experiencing new or worsening temperature numbness, it warrants a prompt clinical evaluation by a neurologist or neurosurgeon. Symptoms alone do not prove that a syrinx is actively expanding, but they are a sign that an updated assessment is needed. Your doctor will likely recommend an MRI of your brain and spine to check the size of the syrinx and look for other potential causes ^[11][12]. They may also use cine phase-contrast MRI, a specialized motion-sensitive scan that estimates how your cerebrospinal fluid is moving ^[12].

Treatment decisions are highly individualized based on symptoms, imaging, and causes. Surgery (such as a Chiari decompression) may be considered to improve CSF flow and stop the nerve damage from getting worse ^[11][13]. However, surgery is not guaranteed to restore temperature sensation that has already been lost, and some stable or minimally symptomatic cases are safely monitored over time without surgery.

Red Flag Symptoms: Seek emergency medical care rather than waiting for a routine appointment if you experience sudden or rapidly progressive weakness, a new inability to walk, a sudden loss of bowel or bladder control, or severe new difficulty breathing or swallowing.