Neurology billing relies on precise ICD-10 diagnosis coding to reflect complex disorders of the brain, spinal cord, peripheral nerves, and neuromuscular system. Neurological conditions often involve chronic disease management, overlapping symptoms, and varying levels of severity. All of these must be clearly documented and accurately coded.
When ICD-10 codes lack specificity or do not align with clinical documentation, payers deny claims, delay reimbursement, or request additional records. For a practice already stretched thin, those denials mean lost revenue and wasted staff time.
This guide covers the most common ICD-10 codes for neurology in 2026, including updates for multiple sclerosis codes. You will learn what changed, how to select the right code, and what documentation supports medical necessity for both office visits and diagnostic testing.
Migraine ICD-10 Codes (G43)
Migraine coding appears easy until you read the documentation. You’ll see a note that reads “migraine headache”, and you’ll think you’ve completed your work. You haven’t yet. The code requires four distinct components: the type of migraine, whether aura was present, whether the migraine is intractable, and whether status migrainosus is also present. You cannot omit any of these; otherwise, you’re left with a nonspecific code.
Over the years, the g43 classification has evolved to provide coverage for all types of migraine disorders:
- G43.0 – migraine without aura. The code applies to classic migraines wherein the patient does not experience visual/sensory disturbances prior to the headache onset.g43.1 – migraine with aura. Basilar migraine, classical migraine, and migraine equivalents are included within this category.
- G43.4 – Hemiplegic migraine. This represents a rare subtype characterized by transient motor weakness.
- G43.5 – persistent aura without infarction. Symptoms resulting from the aura persist for longer than seven days and no stroke occurred.
- G43.6 – persistent aura with infarction. The aura caused a stroke.
- G43.7 – chronic migraine. Applies to patients experiencing headaches at least fifteen times monthly.
- G43.8 – other migraine. Used for migraines which don’t fall into another category.
- G43.9 – unspecified migraine. When documentation doesn’t allow for specification, this is your backup.
Codes you will use more frequently than others:
- G43.909 – unspecified migraine, not intractable without status migrainosus. You frequently use this code when your provider does not detail the type of migraine. It is the go-to code for regular follow-ups when the patient is stable and the provider is simply filling prescriptions. Approximately sixty to seventy percent of claims include this code.
- G43.1 – migraine with aura. Herein lies the problem with this code. G43.1 is considered a parent code. Therefore, you should only use it when the documentation does not support any further specificity. If your provider writes “typical aura” in relation to a migraine, you should be using the more specific code found underneath g43.1. Those days of simply assigning g43.1 to a claim and going about your business are now behind us.
The 2026 specificity snare
Using the most specific code possible is essential for migraine coding. For instance, g43.1 encompasses basilar migraine, classical migraine, migraine equivalents, and typical aura migraines. The icd-10 official guidelines explicitly state that you cannot use g43.1 for payment purposes because there exist multiple codes below it with greater specificity.
To illustrate this point in a practical sense: your provider writes “migraine with aura”. While writing that provides enough information to assign g43.1, it does not provide enough information regarding the specific nature of the aura experienced by the patient. Did he/she experience typical aura? Basilar-type aura? Hemiplegic-type aura? Documentation must substantiate the specific code.
Intractability: what does it mean and why does it matter?
Intractable refers to the fact that the migraine is not responsive to treatment. The documentation must demonstrate that the provider has demonstrated that standard treatments have either failed or are ineffective. If your provider has written “treatment-resistant,” “pharmacoresistant,” “refractory,” “poorly-controlled,” or similar terminology in reference to the patient’s migraine treatment response, then you can use the intractable code.
The intractable versions of the codes differ from their non-intractable counterparts based upon a single digit in the fifth position. To illustrate, g43.909 is non-intractable, while G43.919 is intractable. one single-digit difference makes two entirely different codes.
Documentation checklist for migraine
When reading through the documentation, you want to ensure that you find the following components:
- type of migraine (with aura, without aura, chronic, etc.)
• the specifics of the aura (if present)
• intractability (whether the migraine is unresponsive to treatment)
• status migrainosus (is status migrainosus present?)
• frequency/severity
• did any diagnostic testing occur (e.g., eeg/mri)?
Epilepsy icd-10 codes (g40)
Medical Billing for Epilepsy is arguably the most detail-oriented aspect of Neurology billing. The g40 classification applies to Epilepsy and recurring seizures. Within the classification, codes are grouped by seizure type, intractability and presence/absence of status epilepticus. Over three dozen codes exist, and each code contains its own definitions.
Unfortunately, many providers do not adequately describe the type of seizure experienced by their patients in their documentation. They write “seizure disorder” leaving you to interpret the rest. Simply put, this is insufficient. You need to determine if the seizures were localized/focal or generalized. Furthermore, you need to identify if they are idiopathic or symptomatic. Finally, you need to establish if the seizures are intractable.
Code classifications overview
Below are examples of classifications:
- G40.0 — Localization-related (focal) idiopathic Epilepsy: these classifications apply to seizures originating in one area of the brain and whose causes are unknown (idiopathic).
Examples of classifications include benign childhood Epilepsy with centrotemporal spikes. - G40.1 — Localization-related (focal) symptomatic Epilepsy with simple partial seizures: simple partial seizures do not impair consciousness; therefore, awareness persists during episodes.
- G40.2 — Localization-related (focal) symptomatic Epilepsy with complex partial seizures: complex partial seizures cause impairment of consciousness; typically causing staring or performing automatic movements.
- G40.3 — generalized idiopathic Epilepsy and epileptic syndromes: seizures begin affecting both sides of the brain simultaneously; includes juvenile myoclonic Epilepsy and childhood absence Epilepsy.
- G40.4 — other generalized Epilepsy and epileptic syndromes: includes Epilepsy with myoclonic absences and Epilepsy with myoclonic-astatic seizures.
G40.a — absence epileptic syndrome: petit mal seizures are classified as such.
G40.b — juvenile myoclonic Epilepsy: represents a particular genetic Epilepsy syndrome.
G40.c — Lafora progressive myoclonus Epilepsy: rare, progressively deteriorating form of Epilepsy.
Common codes
- G40.909 — Epilepsy unspecified not intractable without status epilepticus: this is the generic code used when documenting seizure disorder management and documentation does not contain sufficient detail regarding the type(s) of seizures experienced by the patient. I commonly observe this code being applied across numerous claims; truthfully, it is grossly overused. Utilizing a more accurate code reduces likelihood of scrutiny of claims.
- G40.919 — Epilepsy unspecified intractable without status epilepticus: documented when evidence exists showing that treatment attempts have failed due to ineffectiveness or poor responses.
- G40.a09 — absence epileptic syndrome not intractable without status epilepticus: classified as petit mal seizures; when your provider documents “absence seizures” or “petit mal Epilepsy,” utilize this code.
Codes designated for status epilepticus
Status epilepticus is considered a medical emergency; it is defined as prolonged seizure activity or sequential seizures without intervening recovery periods. The codes differentiate between presence and absence of intractability and status epilepticus.
Simple structure regarding code organization
Once familiarized with its structure:
- g40.xxx1 — with status epilepticus
• g40.xxx9 — without status epilepticus
G40.909 denotes Epilepsy unspecified not intractable without status epilepticus whereas G40.919 indicates Epilepsy unspecified intractable without status epilepticus.
Important intractability definition you must understand
As indicated previously, the icd-10 classification system defines certain terms as synonymous with intractability: pharmacoresistance, pharmacological resistance, treatment resistance, refractory, medically refractory and poorly-controlled. As long as your provider utilized any of these terms in describing treatment effectiveness/response; you can utilize the intractable version of the code.
Many coders overlook this rule and continue to apply G40.909 regardless of whether their provider wrote “refractory Epilepsy”.
Excludes notes that are commonly misinterpreted
A couple of excludes that surprise some coders:
- Conversion disorder w/seizures (f44.5): this is a psychiatric illness, not Epilepsy.
• unspecified convulsion (r56.9): use this when seizure type is unspecified as Epilepsy.
• seizure posttrauma (r56.1): use when seizure follows head injury.
• newborn seizure (p90): use when referring to seizures occurring in neonates.
Documentation checklist for Epilepsy
While reviewing documentation, seek the following details:
- Epilepsy type (localized/focal vs generalized vs absence vs etc.)
• seizure type (simple partial vs complex partial vs tonic clonic vs etc.)
• symptomatic idiopathic Epilepsy (was Epilepsy caused by something or did cause occur naturally?)
• intractability (were seizures unable to be controlled through medication/treatment)
• status epilepticus (did status epilepticus occur?)
Neuropathy ICD-10 Codes (G60-G62)
Neuropathy coding encompasses a range of peripheral nerve disorders, such as polyneuropathies, hereditary neuropathies, and inflammatory neuropathies. While the symptoms may overlap among these various conditions, the coding process relies heavily upon identifying the underlying cause of the neuropathy.
G60 – hereditary and idiopathic neuropathy
Charcot-Marie-Tooth disease and other genetic neuropathies fall into this category. G60.9 – hereditary and idiopathic neuropathy, unspecified. Use this code when the type is not identified. As a result, many cases of neuropathy of undetermined origin will be assigned this code.
G61 – inflammatory polyneuropathy
Guillain-barré syndrome (gbs) and chronic inflammatory demyelinating polyneuropathy (CIDP) are examples of inflammatory neuropathies. G61.0 – guillain-barré syndrome. This code is designated for acute inflammatory demyelinating polyneuropathy. G61.81 – chronic inflammatory demyelinating polyneuritis (CIDP). A specific code for CIDP, because treatments differ and outcomes vary based on the type of neuropathy. G61.89 – other inflammatory polyneuropathies. G61.9 – inflammatory polyneuropathy, unspecified.
G62 – other polyneuropathies
Toxic, drug-related, and metabolic neuropathies fall into this category. G62.9 – polyneuropathy, unspecified. Although this is the most commonly used code for peripheral neuropathy, do not use when a more specific cause is documented.
Most frequently used codes
G62.9 – polyneuropathy, unspecified. This code will be frequently used for peripheral neuropathy management when the cause is unclear. G61.81 – chronic inflammatory demyelinating polyneuritis (CIDP). Use for patients diagnosed with CIDP who require IVIG or steroid therapy. G60.9 – hereditary and idiopathic neuropathy, unspecified. Use for presumed genetic neuropathies.
Documentation needed for coding
Documentation of the type of neuropathy; cause; and extent/distribution is required for accurate neuropathy coding. Diabetic neuropathy, for example, uses two separate codes: one for diabetes (e11.40); and another for the type of neuropathy. Do not use G62.9 for diabetic neuropathy. Use both.
If the provider states “peripheral neuropathy,” identify the cause: diabetic? Toxic? Genetic? The cause dictates the code.
ICD-10 codes for multiple sclerosis (g35)
A major change is coming to MS coding in 2026. Single code g35 will be eliminated. You cannot simply write g35 anymore. Choose a specific code based on the type of MS.
New structure
G35.a – relapsing-remitting multiple sclerosis. This is the most common form of MS where patients experience episodes (relapses) of increased disability separated by periods of improvement (remissions).
G35.b – primary progressive multiple sclerosis. The disease progresses at onset without relapses or remissions.
G35.b0 – primary progressive multiple sclerosis, unspecified. Use when the activity status of the disease is not reported.
G35.b1 – active primary progressive multiple sclerosis. Use when there is evidence of ongoing disease activity.
G35.b2 – non-active primary progressive multiple sclerosis. Use when the disease has stabilized.
G35.c – secondary progressive multiple sclerosis. This occurs when the disease starts as relapsing-remitting MS, but eventually becomes progressive.
G35.C0 – secondary progressive multiple sclerosis, unspecified.
G35.c1 – active secondary progressive multiple sclerosis.
G35.c2 – non-active secondary progressive multiple sclerosis.
G35.D – multiple sclerosis, unspecified. Use only when the type of MS is not specified. This should be your last option.
Old code g35 was general-purpose. It did not differentiate between various forms of MS that have unique treatment options and prognostics. The new structure provides a method for documenting and tracking disease progression and responses to treatment.
This is not simply a change in how we report our findings — it is also a change in what we are reporting. Reporting must include both the type of MS and current disease activity. Simply stating “MS” is insufficient to warrant assignment of g35.
Coding tips for MS
Identify the type of MS in the assessment section of your notes. Relapsing remitting vs. Secondary progressive are very different. Identify whether the disease is currently active or in remission based on recent relapse history or stabilization. Both are important to assigning the correct code.
According to ICD-10 criteria, the classification system identifies three main categories of MS: relapsing-remitting; primary progressive; and secondary progressive, with sub-codes designating active and inactive disease patterns. These levels of detail are critical for making informed treatment decisions, since different disease modifying medications are approved for use depending on the type of MS and its pattern of disease progression.
Consequences of not adhering to this requirement
If you continue to use g35, your claims will be denied. The old g35 code has become a parent code for these more specific codes. Therefore, you must choose a more specific code based on your documentation.
Parkinson’s disease ICD-10 codes (g20)
A code that should be familiar to you
Parkinson’s disease coding is relatively easy compared to other areas of neurology. There is only one primary code for parkinson’s disease: g20. The g20 code covers hemiparkinsonism, idiopathic parkinssonism, paralysis agitans; and any other variation of parkinson’s disease.
Structure
G20 – parkinson’s disease. This code applies to all variations of parkinson’s disease; e.g., hemiparkinsonism; idiopathic parkinsonism; paralysis agitans. Billable code
Change in 2026:
The g20 code has been expanded to include a variety of clinical presentations; therefore, it is a parent code similar to g35 in MS coding in 2026. Use a more specific code whenever possible.
Required documentation
Specify the type of parkinsinism.
Was it caused by idiopathic parkinson’s disease? Or some other factor? Specify the severity of parkinson’s if applicable.
Are there complications? dyskinesia? Falls?
Related codes
- g21.– secondary parkinson’s (e.g., drug induced post-infectious etc.)
• g21.1– other drug-induced secondary parkinson’s
• g22.– parkinson’s in diseases classified elsewhere
• g23.– degenerative basal ganglia diseases other than those listed above
Symptoms vs diagnostic codes: when to report each
Use symptom codes during initial evaluation only!
Report symptom codes only during the initial evaluation period while awaiting confirmation of a final diagnosis. Replace symptom codes with condition-specific codes as soon as a confirmed diagnosis is made!
- r20.2 – Paresthesia of skin (numbness/tingling)
• r42 – dizziness/giddiness
• r51 – headache
• r25.3 – fasciculations
• r41.82 – altered mental status
• r27.0 – Ataxia (unspecified)
• r26.8 – abnormalities of gait/mobility
These symptom codes are useful for documenting the evaluation process leading up to establishing a diagnosis of a neurological condition; however, if you continue to report symptom codes past the third encounter, you’re failing in your responsibilities as a coder! By that time, a diagnosis should have been established.
Differential diagnosis codes
Codes below apply to specific types of conditions/diseases:
- g44.88 – headache due to trauma & /or injury of head and/or neck
• G44.841 – whiplash headache
• G44.810 – subarachnoid hemorrhage headache
• G44.812 – giant cell arteritis headache
• G44.820 – idiopathic intracranial hypertension headache
• G44.822 – headache due to brain tumor
• G44.847 – trigeminal neuralgia headache
• G44.848 – atypical facial pain headache
• G44.85 – other cranial neuralgia headaches
Billing Implications and Best Practices in Neurology Medical
Payers review all neurological claims for medical necessity using the ICD-10 diagnosis codes to determine if they support the services billed. Denials occur when the ICD-10 codes submitted for reimbursement are too general; do not match the indication for the service performed; or do not demonstrate medical necessity.
Example: EEGs for seizure management need a code indicating a seizure disorder. A headache code cannot justify an EEG. An EMG for neuropathy requires a neuropathy code. A back pain code can’t justify an EMG.
Using Too Many Unspecified Codes Can Lead To Scrutiny By Payers
While unspecified codes may be acceptable at times, excessive usage by payers will lead to increased scrutiny. The greater detail within a code, the lesser likelihood there will be a claim denial.
Example: Instead of using G43.909 (migraine, unspecified) as often as possible, use G43.0 (migraine without aura) or G43.1 (migraine with aura). Use G40.- (epilepsy) with the correct seizure type modifier. Use G31.7 (multiple sclerosis) with either G31.71 (relapsing-remitting MS); G31.72 (primary progressive MS); G31.73 (secondary progressive MS); or G31.79 (MS, unspecified). The more detail in the code entered, the less likely there will be a denial. This applies to both medical necessity justification and payment.
Ensure There’s Sufficient Correlation Between Diagnostic Testing And The Diagnosis Codes
ICD-10 codes need to correlate with the advanced imaging and diagnostic testing ordered. An MRI for headache should include a headache diagnosis. An EEG for seizure management should have a seizure disorder diagnosis. When there is no correlation between the ICD-10 codes and the diagnostic testing ordered, it results in denials.
Why The 2026 Multiple Sclerosis Coding Changes Must Be Prioritized
Multiple Sclerosis is one of the greatest changes from 2015 to 2026. The old code G35 is no longer billable. Any practice that doesn’t adjust their documentation and billing systems will experience denials.
FAQS
What is the ICD-10 code for Neuropathy?
There are two main codes, G62.9 (Polyneuropathy, unspecified) and G60.9 (Hereditary and Idiopathic Neuropathy) for various forms of neuropathy. Chronic Inflammatory Demyelinating Polyneuritis has its own code G61.81.
What is the ICD-10 code for Multiple Sclerosis?
G35 is the parent code. With the new 2026 coding system, you’ll be required to use the more specific codes such as G35.A (Relapsing-Remitting MS); G35.B (Primary Progressive MS); G35.C (Secondary Progressive MS); and G35.D (MS, unspecified).
What is the ICD-10 code for Migraine?
G43.909 (Migraine, unspecified) is frequently used. However, depending upon the specifics of the patient’s condition, you might want to consider using more specific codes such as G43.0 (Migraine without Aura); or G43.1 (Migraine with Aura).
What is the ICD-10 code for Epilepsy?
G40.909 (Epilepsy, unspecified) is also very commonly used. Depending upon how the physician documents the patient’s seizures, you’ll probably want to use a more specific code than this. Such as, G40.- with the correct seizure type modifier; G40.-1XA (Status Epilepticus, Active); or G40.-2XN (Seizures, Non-Intractable).
What happened in 2026 with Multiple Sclerosis coding?
The single code G35 was replaced with more specific codes to reflect different types of MS and disease activity levels. Specifically, Relapsing-Remitting; Primary Progressive; Secondary Progressive MS; and Subcodes for Active vs Non-Active Disease Activity were added. You must begin using these new codes immediately.
Conclusion
Coding for neurology under ICD-10 is complex; however, it is certainly manageable. As mentioned earlier, due to the significant changes made to coding for MS in 2026, practices need to address these immediately. G35 is no longer billable. Practices will need to use the new more specific codes to bill appropriately.
Need Help Reducing Neurology Coding Errors and Claim Denials?
Accurate neurology ICD-10 coding is only one part of successful reimbursement. Clean clinical documentation, correct CPT-ICD-10 pairing, payer-specific billing rules, and proactive denial management all play a role in getting claims paid the first time.
At UControl Billing, our certified medical billing and coding specialists help neurology practices improve billing and coding accuracy, reduce denials, accelerate reimbursements, and strengthen overall revenue cycle performance. From ICD-10 coding support and claim submission to payment posting, A/R follow-up, and denial management, we provide end-to-end billing solutions tailored to your specialty.
Contact UControl Billing today to learn how our neurology medical billing experts can help your practice improve cash flow while reducing administrative workload.
