Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is a rare, acquired autoimmune disorder affecting the peripheral nervous system. The body’s immune system mistakenly attacks the myelin sheath, the protective covering around nerve fibers. This damage disrupts electrical signal transmission, causing symptoms like muscle weakness and sensory loss. Since CIDP is treatable, an early and accurate diagnosis is important to prevent permanent nerve damage. Diagnosis involves a careful series of steps, starting with clinical observation and moving through specialized electrophysiological and laboratory tests.
Initial Clinical Assessment
The diagnostic process begins with a detailed review of the patient’s medical history and a thorough physical examination. The pattern and progression of symptoms are the first indicators that raise suspicion for CIDP. A key feature is symmetrical muscle weakness, often involving both the proximal muscles (shoulders and hips) and the distal muscles (hands and feet).
Patients typically report difficulty with tasks like climbing stairs, rising from a chair, or lifting objects overhead. Sensory symptoms, such as tingling, numbness, or a loss of vibration and position sense, are also commonly reported in a “stocking-glove” pattern. A hallmark physical finding is the diminished or complete absence of deep tendon reflexes, known as areflexia or hyporeflexia, across all four limbs.
The timeline of symptoms is a defining factor that distinguishes CIDP from its acute counterpart, Guillain-Barré Syndrome (GBS). For a diagnosis of CIDP, the muscle weakness and sensory changes must have developed and progressed over a minimum duration of eight weeks. This chronic progression, whether it is slowly worsening or relapsing and remitting, establishes the long-term nature of the condition.
Electrophysiological Testing
Following the clinical assessment, electrophysiological testing provides objective evidence of the nerve damage characteristic of CIDP. Nerve Conduction Studies (NCS) and Electromyography (EMG) are the primary tools used in this stage. NCS involves stimulating nerves with small electrical pulses and recording the speed and strength of the resulting signal.
The results of the NCS demonstrate the presence of demyelination. Specific findings include a significant slowing of the nerve conduction velocity, indicating that the myelin insulation is damaged. Prolonged distal latencies, the time it takes for the signal to travel from the stimulation point to the muscle, are also frequently observed.
Another finding is the presence of partial motor conduction block, where the signal amplitude significantly drops along a segment of the nerve, indicating the impulse cannot fully pass the damaged area. Temporal dispersion occurs when a nerve signal spreads out in time as it travels, reflecting the fact that individual nerve fibers are conducting at different, slower speeds. Electromyography, using a needle inserted into the muscle, assesses the electrical activity of the muscle fibers themselves, helping to determine the extent of secondary muscle damage and to exclude other primary muscle diseases.
Supporting Laboratory Investigations
While electrophysiological tests confirm nerve dysfunction, laboratory investigations are necessary to exclude conditions that can mimic CIDP. A common procedure is the lumbar puncture, or spinal tap, to analyze the cerebrospinal fluid (CSF). In approximately 80 to 90 percent of typical CIDP cases, the CSF analysis reveals a finding known as albuminocytologic dissociation.
This dissociation means there is an elevated protein level in the CSF, primarily albumin, but a normal or near-normal white blood cell count. The increased protein is thought to be a result of inflammation in the nerve roots allowing proteins to leak into the CSF. Finding a high number of white blood cells in the CSF, however, would suggest an alternative diagnosis, such as an infection or another inflammatory disorder.
Blood tests are performed to rule out other causes of polyneuropathy. These investigations check for conditions like diabetes, thyroid dysfunction, vitamin B12 deficiency, or the presence of a monoclonal gammopathy. Testing for infectious causes such as HIV or Lyme disease is also standard. These laboratory results help confirm if the neuropathy is idiopathic—of unknown cause—or secondary to a known underlying condition.
Applying Formal Diagnostic Standards
The final step in the diagnosis of CIDP involves synthesizing all the collected clinical, electrophysiological, and laboratory data according to internationally recognized medical guidelines. The most widely used framework is provided by the European Academy of Neurology and the Peripheral Nerve Society (EAN/PNS). These guidelines provide specific criteria for classifying the condition.
The guidelines use the strength of the electrodiagnostic evidence to categorize the diagnosis into two main levels: “CIDP” or “possible CIDP.” A diagnosis of CIDP requires meeting specific thresholds for demyelinating features in a certain number of nerves. If the electrophysiological evidence is inconclusive, the diagnosis may remain “possible CIDP” unless supportive criteria are met.
These supportive criteria can include the characteristic albuminocytologic dissociation in the CSF, evidence of nerve root enhancement on a spinal Magnetic Resonance Imaging (MRI), or a clear, objective response to CIDP-specific treatment. The diagnosis of CIDP is not based on a single test result but is a clinical decision. It requires an experienced neurologist to weigh all the evidence, rule out alternative diagnoses, and align the patient’s presentation with established diagnostic criteria.