Timothy C. Hain, MD, Chicago IL.• Page last modified: April 14, 2020
Dizziness is a "sorting problem" for doctors, as it is a subjective symptom that can be caused or associated with many disorders.
General categories for dizziness include:
There are no diagnostic tests for many of these entities, and for this reason, many of which are assigned based on the consensus of a committee, rather than (for example), a blood test or X-ray finding.
Usually the situation is that there is a group of people who feel that they are experts, meet periodically, publish lists of symptoms, and suggest that individuals that endorse these particular symptoms, have a "disease". Nearly always, one can recognize these disorders, because the publication that describes the criteria, says that everything else must be excluded first. We call this a "wastebasket" diagnosis. In the present day/age, one might also term this a "google" diagnosis - -i.e. someone who can read the symptom list on google, can endorse the symptoms of committee diagnoses. A good clue that a diagnosis is a "committee diagnosis", is that the frequency of the diagnosis varies remarkably in different parts of the world. This is not so much the case for brain tumors (for example).
Competition between committee diagnoses
To make things worse: It is common for several committees, generally in different medical disciplines, to "claim" the same symptom collection -- causing overlap and contention for a collection of symptoms. In the dizziness area, overlapping symptom collections include vestibular migraine, PPPD, and mal de debarquement. When there are overlapping symptom inventories, the "diagnosis", the label for a set of subjective symptoms, becomes negotiable.
There is nothing "wrong" about committee diagnoses, but one must realize that they are not on as firm grounds as diagnoses based on objective evidence. Taking a cynical perspective, if you ask what these diagnoses are good for, It can be easier for a provider to attribute a disorder to a "committee" diagnosis, than just to say that they have no idea why the patient is complaining about dizziness, or perhaps, hasn't responded to that provider's treatment. More kindly, these committee diagnoses certainly provide a naming system under which to accumulate information about prognosis and treatment.
The psychiatric community is tolerant to committee diagnoses, as their entire field is built on collections of symptoms. The psychiatric "committee" document is called the "DSM" -- diagnostic statistical manual. Thus, one major group of "committee" diagnoses are psychiatric disorders of nearly any type. A new psychiatric committee diagnosis relevant to dizziness is "Chronic Subjective Dizziness", or CSD. CSD also goes by the name of PPV and PPPD. Somatization disorder is another broadly drawn psychiatric condition, defined by a committee. All of these overlap hugely.
The Neurological community's "big" committee diagnosis is Migraine. The migraine committee is called the IHS - -or International Headache Society. About 15% of the population has "migraine", and the IHS description of headache symptoms now extends to 160 pages, and about 130 symptom patterns. The IHS meets frequently. There has been some attempt to move migraine out of the committee realm into the evidence based diagnosis realm, but they always fail. For example, attempts to find the "migraine gene" always succeed, but nearly always find different genes (: Migraine seems to be a collection of many illnesses, with similar symptoms. Recently, another committee has been mobilized to assist the IHS with dizziness - -the Barany society has developed committees of it's own, that work with the IHS. Again somewhat curiously, migraine has been growing more popular in recent years, and has taken over some of the territory of Sinus headache (Eros et al, 2007).
Similar to migraine, a motion sickness variant (mal de debarquement syndrome) is also a committee diagnosis.
There are many conditions in Neurology that generally do require objective data to make a firm diagnosis - -for example multiple sclerosis, or stroke.
The otolaryngologists, or otologists, have far less committee illnesses relating to dizziness. The American Academy of Otolaryngology (AAO) Meniere's committee met only twice, and has not met at all recently. Their description document is small (about 5 pages total), compared to the 160 or so pages describing the "headache" diagnostic criteria put forth by the international headache society.. Far less people meet the Meniere's criteria than migraine - -roughly 1/2000 of the population rather than roughly 1/6 of the population with migraine. The "eye of the needle" in Meniere's is that one has to fail a hearing test. This greatly narrows the field of possibilities. There is presently some competition going on between vestibular migraine and Meniere's disease, as there is considerable overlap in symptoms.
Most fields have their committee diagnoses, that frequently overlap with other field's committee diagnoses. Rheumatology, for example, has "fibromyalgia", which overlaps with migraine.
There are some "orphan" disorders that so far, have no committees to validate their existence. An example of this is "cervical vertigo", which has a good physiological underpinnings, but lacks a committee to define its symptoms. We think that it is reasonable to expect that somewhat objective tests for cervical vertigo will emerge.
To summarize so far -- Dizziness is largely subjective, and many medical committees have attempted to define illnesses that include dizziness. Committee illnesses are intrinsically vulnerable to the "lumping" error - -many distinct entities may be "lumped" into a single pseudo-illness.
For these symptom inventories, the goal is to generally to reduce symptoms using some intervention. Perhaps we can work out a way to go from symptoms/data to treatment, and skip the diagnosis part. Computer technology such as "big data", and "neural networks", have the potential to cut out the middleman (the diagnosis), and just go from a pattern to a treatment.