Genetic testing is necessary to identify the syndrome. The DNA test is necessary sometimes because symptoms may not be sufficient to definitely diagnose this condition.

Between this condition and NF-1 an important difference is the absence of tumor growths (Lisch nodules and neurofibromas which are common in NF-1) in LS.

The symptoms of Legius syndrome and NF-1 are very similar, this is the reason why the two are easily confused. A genetic test is often the only way to make sure a person has LS and not NF-1,

the similarity of symptoms stem from the fact that the different genes affected in the two syndromes code for proteins that carry out a similar task in the same reaction pathway.

Ferner et al. give the following diagnostic criteria for Schwannomatosis:

- Definite

- Age >30 years and ≥2 nonintradermal schwannomas, at least one with histologic confirmation and no evidence of vestibular tumor on MRI scan and no known NF mutation, or

- One nonvestibular schwannoma plus a first-degree relative with schwannomatosis

- Possible

- Age <30 and ≥2 nonintradermal schwannomas, at least one with histologic confirmation and no evidence of vestibular tumor on MRI scan and no known NF mutation, or

- Age >45 and ≥2 nonintradermal schwannomas, at least one with histologic confirmation and no symptoms of 8th nerve dysfunction and no NF2, or

- Nonvestibular schwannoma and first-degree relative with schwannomatosis

- Segmental. Diagnosed as definite or possible but limited to one limb or ≤5 contiguous segments of spine.

Another set of criteria are:

- Two or more nonintradermal (cutaneous) schwannomas

- No evidence of vestibular tumor

- No known NF-2 mutation

or

- One pathologically confirmed nonvestibular schwannoma plus a first degree relative who meets the above criteria.

Prenatal testing may be used to identify the existence of NF-1 in the fetus. For embryos produced via in vitro fertilisation, it is possible via preimplantation genetic diagnosis to screen for NF-1.

Chorionic villus sampling or amniocentesis can be used to detect NF-1 in the fetus.

People with NF-1 have a 50% percent chance of passing the disorder on to their kids, but people can have a child born with NF-1 when they themselves do not have it. This is caused in a spontaneous change in the genes during pregnancy.

Plain film

often seen as a lobulated, eccentric radiolucent lesion

long axis parallel to long axis of long bone

no periosteal reaction (unless a complicating fracture present)

geographic bone destruction: almost 100%

well defined sclerotic margin: 86%

there can be presence of septations (pseudotrabeculation): 57% 2

there can be presence of matrix calcification in a small proportion of cases: 12.5%1

MRI

MR features are often not particularly specific. Signal characteristics include

T1 - low signal

T1 C+ (Gd) -

the majority (~70%) tend to show peripheral nodular enhancement

~ 30% diffuse contrast enhancement and this can be either homogeneous or heterogeneous 19

T2 - high signal

Bone scan

A scintigraphic "doughnut sign" has been described in this tumour type 11. However, this is very non-specific and can be found in a plethora of other bone lesions.

They are benign lesions and malignant degeneration is rare. They are usually treated with curettage which however have a high recurrence rate of 25%. As such if an en-bloc resection is possible this is advisable

The National Institutes of Health (NIH) has created specific criteria for the diagnosis of NF-1. Two of these seven "Cardinal Clinical Features" are required for positive diagnosis. There is practical flowchart to distinguish between NF1, NF2 and schwannomatosis.

- Six or more café-au-lait spots over 5 mm in greatest diameter in pre-pubertal individuals and over 15 mm in greatest diameter in post-pubertal individuals. Note that multiple café-au-lait spots alone are not a definitive diagnosis of NF-1 as these spots can be caused by a number of other conditions.

- Two or more neurofibromas of any type or 1 plexiform neurofibroma

- Freckling in the axillary (Crowe sign) or inguinal regions

- Optic glioma

- Two or more Lisch nodules (pigmented iris hamartomas)

- A distinctive osseous lesion such as sphenoid dysplasia, or thinning of the long bone cortex with or without pseudarthrosis.

- A first degree relative (parent, sibling, or offspring) with NF-1 by the above criteria.

Schwannomatosis can not presently be diagnosed prenatally or in the embryo, because the gene for it has not yet been positively identified.

ONSM does not improve without treatment. In many cases, there is gradual progression until vision is lost in the affected eye. However, this takes at least several months to occur, and a minority of patients remain stable for a number of years.

Clinical examination will show an abnormal optic disc, either swollen or atrophic. Optociliary shunt vessels may be seen; the combination of these with progressive visual loss and optic disc atrophy is known as the Hoyt-Spencer triad. Visual acuity is usually but not always reduced.

When ONSM is suspected, MRI of the brain or orbits should be performed. This will usually show characteristic findings and confirm the diagnosis.

With the symptoms above in mind, practitioners would likely look for decreased vision and intraocular masses in making their diagnosis as these have been documented as the most common findings for intraocular schwannomas. Additionally, these tumors are most frequently found in the choroid, at 60%, as compared to the ciliary body (40%) and the iris (11%). Schwannomas generally present themselves as smooth, ovoid masses, lacking pigmentation. However, these tumors can also rarely be colored and lobulated. This overlap can lead to a uveal melanoma diagnosis as these can be characteristics of both.

While the clinical picture may point towards the diagnosis of the Roussy–Lévy syndrome, the condition can only be confirmed with absolute certainty by carrying out genetic testing in order to identify the underlying mutations.

The diagnosis of salivary gland tumors utilize both tissue sampling and radiographic studies. Tissue sampling procedures include fine needle aspiration (FNA) and core needle biopsy (bigger needle comparing to FNA). Both of these procedures can be done in an outpatient setting. Diagnostic imaging techniques for salivary gland tumors include ultrasound, computer tomography (CT) and magnetic resonance imaging (MRI).

Fine needle aspiration biopsy (FNA), operated in experienced hands, can determine whether the tumor is malignant in nature with sensitivity around 90%. FNA can also distinguish primary salivary tumor from metastatic disease.

Core needle biopsy can also be done in outpatient setting. It is more invasive but is more accurate compared to FNA with diagnostic accuracy greater than 97%. Furthermore, core needle biopsy allows more accurate histological typing of the tumor.

In terms of imaging studies, ultrasound can determine and characterize superficial parotid tumors. Certain types of salivary gland tumors have certain sonographic characteristics on ultrasound. Ultrasound is also frequently used to guide FNA or core needle biopsy.

CT allows direct, bilateral visualization of the salivary gland tumor and provides information about overall dimension and tissue invasion. CT is excellent for demonstrating bony invasion. MRI provides superior soft tissue delineation such as perineural invasion when compared to CT only.

The systemic and ocular prognosis for intraocular schwannoma is positive. While a patient may lose an eye, they are unlikely to encounter metastasized growth or life-threatening malignant change. Although follow-up data has shown the potential need for re-excision and side-effects, these issues are minor and the general outcome for patients is excellent.

Detection of this type of neuropathy has concentrated mostly on detecting presence of antibodies because the antibodies are the main cause for the disease. Anti-MAG antibodies can be readily detected in a patient’s sera using various types of assays, but mainly an ELISA has been shown to be most effective. There are also various biological indicators, such as elevated cerebral spinal fluid proteins and elevated IgM monoclonal levels. These can also be tested either by drawing serum from a patient or by drawing spinal fluid from a spinal tap and testing using an assay or blot.

The severity of symptoms vary widely even for the same type of CMT. There have been cases of monozygotic twins with varying levels of disease severity, showing that identical genotypes are associated with different levels of severity (see penetrance). Some patients are able to live a normal life and are almost or entirely asymptomatic. A 2007 review stated that "Life expectancy is not known to be altered in the majority of cases".

CMT can be diagnosed through symptoms, through measurement of the speed of nerve impulses (nerve conduction studies), through biopsy of the nerve, and through DNA testing. DNA testing can give a definitive diagnosis, but not all the genetic markers for CMT are known. CMT is first noticed when someone develops lower leg weakness, such as foot drop; or foot deformities, including hammertoes and high arches. But signs alone do not lead to diagnosis. Patients must be referred to a physician specialising in neurology or rehabilitation medicine. To see signs of muscle weakness, the neurologist asks patients to walk on their heels or to move part of their leg against an opposing force. To identify sensory loss, the neurologist tests for deep tendon reflexes, such as the knee jerk, which are reduced or absent in CMT. The doctor also asks about family history, because CMT is hereditary. The lack of family history does not rule out CMT, but helps rule out other causes of neuropathy, such as diabetes or exposure to certain chemicals or drugs.

In 2010, CMT was one of the first diseases where the genetic cause of a particular patient's disease was precisely determined by sequencing the whole genome of an affected individual. This was done by the scientists employed by the Charcot Marie Tooth Association (CMTA) Two mutations were identified in a gene, SH3TC2, known to cause CMT. Researchers then compared the affected patient's genome to the genomes of the patient's mother, father, and seven siblings with and without the disease. The mother and father each had one normal and one mutant copy of this gene, and had mild or no symptoms. The offspring that inherited two mutant genes presented fully with the disease.

The definitive diagnosis is by histologic analysis, i.e. and examination under the microscope.

Under the microscope, OKCs vaguely resemble keratinized squamous epithelium; however, they lack rete ridges and often have an artifactual separation from their basement membrane.

On a CT scan, The radiodensity of a keratocystic odontogenic tumour is about 30 Hounsfield units, which is about the same as ameloblastomas. Yet, ameloblastomas show more bone expansion and seldom show high density areas.

Ultrasound-guided FNAC should be performed for verification of SCTC.

There are no specific radiological tests for SCTC verification. However these tests might be useful for identification of tumor borders and in planning of surgery.

EMG test is often performed together with another test called nerve conduction study, which measures the conducting function of nerves. NCV study shows loss of nerve conduction in the distal segment (3 to 4 days after injury). According to NCV study, in axonotmesis there is an absence of distal sensory-motor responses.

A thorough medical history and physical examination, including a neurological examination, are the first steps in making a diagnosis. This alone may be sufficient to diagnose Bell's Palsy, in the absence of other findings. Additional investigations may be pursued, including blood tests such as ESR for inflammation, and blood sugar levels for diabetes. If other specific causes, such as sarcoidosis or Lyme disease are suspected, specific tests such as angiotensin converting enzyme levels, chest x-ray or Lyme titer may be pursued. If there is a history of trauma, or a tumour is suspected, a CT scan may be used.

Radiologically

- Odontogenic Myxoma

- Ameloblastoma

- Central Giant Cell Granuloma

- Adenomatoid odontogenic tumor

Histologically

- Orthokeratocyst

- Radicular cyst (particularly if the OKC is very inflamed)

- Unicystic ameloblastoma

Electromyography (EMG) is a medical test performed to evaluate and record the electrical activity (electromyogram) produced by skeletal muscles using an instrument called electromyograph. In axonotmesis, EMG changes (2 to 3 weeks after injury) in the denervated muscles include:

1. Fibrillation potentials (FP)

2. Positive sharp waves

There are many diagnostic methods that can be used to determine the type of salivary gland tumour and if it is benign or malignant. Examples of diagnostic methods include:

Physical exam and history: An exam of the body to check general signs of health. The head, neck, mouth, and throat will be checked for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.

Endoscopy: A procedure to look at organs and tissues inside the body to check for abnormal areas. For salivary gland cancer, an endoscope is inserted into the mouth to look at the mouth, throat, and larynx. An endoscope is a thin, tube-like instrument with a light and a lens for viewing.

MRI

Biopsy: The removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer.

Fine needle aspiration (FNA) biopsy: The removal of tissue or fluid using a thin needle. An FNA is the most common type of biopsy used for salivary gland cancer, and has been shown to produce accurate results when differentiating between benign and malignant tumours.

Radiographs: An OPG (orthopantomogram) can be taken to rule out mandibular involvement. A chest radiograph may also be taken to rule out any secondary tumours.

Ultrasound: Ultrasound can be used to initially assess a tumour that is located superficially in either the submandibular or parotid gland. It can distinguish an intrinsic from an extrinsic neoplasm. Ultrasonic images of malignant tumours include ill defined margins.