Differential diagnosis

Differential diagnosis - what is it?

A patient usually comes to the doctor with symptoms that he himself cannot attribute to a specific disease. The doctor now has the task of creating a differential diagnosis through a patient discussion, physical and technical examinations.
The differential diagnosis includes diseases that occur with symptoms that are similar or the same as the symptoms described by the patient and must therefore also be taken into account when making the diagnosis.

The differential diagnoses must be based on the Suspected diagnosis be delimited. This is done with the help of so-called differential diagnostics: This includes all examinations that the Exclusion or confirmation serve a disease that is a differential diagnosis to the suspected diagnosis.

A fictitious example: After the patient interview, two possible illnesses can be considered as explanations for the patient's complaints. One of the diseases is accompanied by abnormalities in the ultrasound, the other is not.
So the doctor will use an ultrasound examination to clarify which of the two differential diagnoses is the actual diagnosis.

The more characteristic a symptom of a particular disease, the smaller the number of possible differential diagnoses. In the case of more general symptoms such as fever, however, the number of differential diagnoses is large because many diseases can be accompanied by fever.

How is the differential diagnosis made?

To a Differential diagnosis the doctor begins with a discussion with the patient. During the so-called anamnese the doctor wants to find out what current symptoms the patient has, what previous or chronic illnesses exist and what illnesses exist in the family.

The doctor also needs information about the medication the patient is taking and about his social and professional environment.

All of these things are important so that the doctor can classify the current symptoms and not forget any symptoms or factors that are related to the patient's illness.
Through a detailed Anamnesis interview the doctor can rule out possible diseases and make a suspected diagnosis including alternative differential diagnoses.

The various differential diagnoses have, for example, both similarities and differences in the course or in the described symptoms of the patient.

By a thorough physical examination the doctor finds other symptoms or findings that speak for or against one of the differential diagnoses. Laboratory examinations, ultrasound examinations, X-rays, CT, MRI and other examinations provide further indications for or against a possible differential diagnosis.
Of course, not all examinations are always necessary to identify the patient's disease, because differential diagnoses can gradually be ruled out in the course of the various diagnostic examinations.

A thorough differential diagnosis is particularly important when setting so-called Exclusion diagnoses. These are diagnoses that may only be made if all other possible differential diagnoses have been reliably ruled out through anamnesis, physical examinations and medical examinations.
This is an example Irritable bowel syndrome, which denotes gastrointestinal problems for which no physical cause can be found.

Differential diagnoses of multiple sclerosis

Neuromyelitis optica

The Neuromyelitis optica (NMO, Devic Syndrome) was long considered a sub-form of multiple sclerosis (MS), but it is a disease of its own.
Both diseases have one thing in common demyelinating inflammation (Demarking of the nerve sheaths).
At the NMO, that is above all Spinal cord and the Optic nerve affected.
A long-term inflammation of the spinal cord over three or more segments is typical, causing sensory disturbances and / or paralysis, as well as inflammation of the optic nerve with impaired vision and pain when moving the eyes.

In many cases it is either Spinal cord or the Optic nerve first affected alone. Foci of inflammation can also be detected in the brain in around 50% of NMO patients, but these differ significantly from the foci of inflammation in multiple sclerosis.
Just like MS, most of the time NMO runs bursts, however, the symptoms usually do not resolve spontaneously or completely, as is often the case with MS.

NMO is more severe than MS, and patients are more quickly dependent on outside help.
The NMO can be positive Aquaporin antibodies Differentiated in the blood from other inflammatory demyelinating diseases of the nervous system.
A differentiation from MS is also possible because it is less common with NMO oligoclonal bands can be found in the liquor (nerve water) (in multiple sclerosis 95%, see: Liquid diagnostics in multiple sclerosis).

Acute disseminated encephalomyelitis

The Acute disseminated encephalomyelitis (ADEM) is also an inflammatory disease of the central nervous system that is associated with Demyelinating of the nerve sheaths goes hand in hand.

In contrast to multiple sclerosis, ADEM mainly affects children and young adults and often occurs after an infection, especially of the upper respiratory tract. After a measles vaccination, ADEM occurs with a probability of 1: 1 million, with a measles infection the probability is three times as high and is 1: 1,000.

In contrast to MS, ADEM does not occur in a relapsing manner, but usually occurs once. A repetitive course is rare, with 90% of patients fully recovering from the disease.

ADEM presents with nausea, vomiting, headache, meningism (severe pain when moving the head towards the chest), confusion, and various neurological symptoms that can be very similar to MS.

However, the accompanying symptoms mentioned are rare in MS. They differ in the imaging of the head Distribution pattern of inflammatory lesions in MS and ADEM: The ADEM occurs more in the area of Cerebral cortex and in depths Brain nuclei on, the MS is more about that Ventricular system around.

In addition to imaging, a CSF puncture can help differentiate: In MS, they are oligoclonal bands almost always present, significantly less often with ADEM.

Differential Diagnoses of Depression

Various differential diagnoses of depression are described below.

Somatogenic Depression

Somatogenic depression can be a consequence or an accompanying symptom physical illness occur, it is then called symptomatic depression.
Examples are one Hypothyroidism, high blood pressure, diabetes or cancer. Symptomatic depression can also be called Side effect of medication occur.

Organic depression can be traced back to structural changes in the brain; it occurs, for example, after a stroke or in the context of dementia as a result of brain atrophy.

Recurrent brief depressive disorder

The disease of the recurrent short depressive disorder manifests itself in depressive episodes that last only a few days (two to four days), but recur more frequently.

Psychotic depression

Not only do symptoms of depression occur but symptoms of one as well psychosis up, there is psychotic depression.
The occurrence of delusional ideas is typical: Patients suffer from the delusional, uncorrectable beliefs that they are impoverished, terminally ill or worthless (impoverishment delusion, hypochondriac or nihilistic delusion).


The Dysthymia describes a depressive mood that lasts at least two years. Patients feel tired, depressed, and have trouble sleeping. In addition, there is the feeling of not being good enough.
The difference to depression is the significantly lower severity of the symptoms, which is why patients with dysthymia usually cope with the demands of everyday life, but cannot enjoy their life and find everything to be very exhausting.


Patients under Cyclothymia suffer, suffer from a very unstable moodthat do not occur in relation to particularly positive or negative life events. There are always slightly depressive phases and phases with an elevated, slightly manic mood. The disease begins in young adulthood and medical treatment is usually not necessary.

Seasonal depression

The most popular form of seasonal depression is the Winter depressionwhich mainly affects women. Those affected suffer from lack of drive, tiredness and loss of interests in autumn and winter, but are completely symptom-free in spring and summer. It is treated with light therapy (special 10,000 lux lamp).

Postpartum depression

About 10% of women who have given birth will develop one within the first few weeks after giving birth Postpartum depression.
This can last for several months, but in most cases it is accompanied by mild symptoms of depression and can therefore usually be treated with medication on an outpatient basis.

Anxiety disorders

Anxiety disorders represent an important differential diagnosis of depression, as a Anxiety disorder may be associated with depressive symptoms and depression with various fears. The delimitation should be done by an experienced doctor.