Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (94 page)

TRIGEMINAL NEURALGIA (TIC DOULOUREUX)

   Definition

Trigeminal neuralgia is a sudden, usually unilateral, severe, brief, stabbing, recurrent pain in the distribution of one or more branches of the fifth cranial (trigeminal) nerve.

   Clinical Presentation

Eighty to ninety percent of cases are caused by compression of the trigeminal nerve root, by an artery or vein, leading to demyelination.
¹
Compression may also be caused by vestibular schwannoma (acoustic neuroma), meningioma, epidermoid, or other cyst. Saccular aneurysm or arteriovenous malformations are rare causes of compression. MS may cause demyelination of one or more of the trigeminal nerve nuclei resulting in pain.

   Laboratory Findings

Diagnosis is performed predominantly by neuroimaging (CT or MRI) and electrophysiologic testing. Laboratory findings may assist in identifying MS or herpes zoster. Tissue biopsy may be needed in the diagnosis of schwannoma (see eBook Figure 4-11), meningioma (see eBook Figures 4-13 and 4-15), and cysts.

Reference

1.  Love S, Coakham HB. Trigeminal neuralgia: pathology and pathogenesis.
Brain.
2001;124:2347.

RETROBULBAR NEUROPATHY (OPTIC NEURITIS)

   Definition

Retrobulbar neuropathy is a disorder of the optic nerve resulting in pain behind the affected eye, impaired vision, and rarely blindness.

   Clinical Presentation

Patients with retrobulbar neuropathy may present with a number of causative disorders including MS (demyelinating optic neuritis), ischemia (arteritic or nonarteritic ischemic optic neuropathy), infectious (West Nile virus, catscratch disease, toxoplasma,
Tuberculosis
, and
Cryptococcus
), tumors, and medications (chloramphenicol, ethambutol, isoniazid, penicillamine, phenothiazines, phenylbutazone, quinine, and streptomycin).
^1,2
Postviral infectious optic neuritis may also occur. Less common causes include sarcoidosis and autoimmune diseases such as lupus, Sjögren syndrome, and Wegener granulomatosis.
³
Retrobulbar neuropathy is associated with MS, which ultimately develops in 30–50% of patients with optic neuritis. Ischemic optic neuropathy is the most common etiology in older patients.
⁴
There are two hereditary forms of optic neuropathy: Leber hereditary optic neuropathy and Kjer disease.
^5,6

The diagnosis is based on the elimination of underlying disorders by history and examination including funduscopic evaluation. Neuroimaging (MRI) may help confirm the presence of acute demyelinating disease and MS. Visual-evoked responses may be helpful in determining demyelination.

   Laboratory Findings

Laboratory testing including sedimentation rate, ANA, angiotensin-converting enzyme levels, and serologic test for Lyme disease should be obtained. Lumbar puncture is helpful to rule out multiple sclerosis. CSF may be normal or reveal increased protein and ≤200/μL lymphocytes. Oligoclonal bands may be present. Other testing should be performed to rule out possible infectious agents, toxins, and genetic disorders based on the history of the individual patient.

References

1.  Balcer LJ. Clinical practice. Optic neuritis.
N Engl J Med.
2006;354:1273.

2.  Lee AG, Brazis PW. Systemic infections of neuro-ophthalmic significance.
Ophthalmol Clin North Am.
2004;17:397.

3.  Rabadi MH, Kundi S, Brett D, et al. Neurological pictures. Primary Sjögren syndrome presenting as neuromyelitis optica.
J Neurol Neurosurg Psychiatry.
2010;81:213.

4.  Hayreh SS. Posterior ischaemic optic neuropathy: clinical features, pathogenesis, and management.
Eye (Lond).
2004;18:1188.

5.  Lamirel C, Cassereau J, Cochereau I, et al. Papilloedema and MRI enhancement of the prechiasmal optic nerve at the acute stage of Leber hereditary optic neuropathy.
J Neurol Neurosurg Psychiatry.
2010;81:578.

6.  Alexander C, Votruba M, Pesch UE, et al. OPA1, encoding a dynamin-related GTPase, is mutated in autosomal dominant optic atrophy linked to chromosome 3q28.
Nat Genet.
2000;26:211.

AUTONOMIC NEUROPATHY

   Definition

Autonomic neuropathy is a group of diseases or syndromes affecting the parasympathetic and/or the sympathetic nerves. It can be hereditary or acquired.

   Clinical Presentation

A wide range of symptoms affecting many different organ systems can occur, including the cardiovascular, GI, GU, pulmonary, and neuroendocrine systems. The most common cause of autonomic neuropathy is DM
¹
(see also Polyneuropathy and the section on Autoimmune Disorders of the CNS).

Disorders that may cause autonomic dysfunction include amyloidosis, Guillain-Barré syndrome, hereditary neuropathies, infections (e.g., Chagas disease, HIV, botulism, diphtheria, and leprosy), toxicities including drugs (vincristine, cis-platinum, Taxol, thallium, and heavy metals), collagen vascular disease (e.g., Sjögren disease, systemic lupus, RA), porphyria, uremia, alcoholic neuropathy, hepatic disease, paraneoplastic syndromes, Lambert-Eaton syndrome, and medications (antihypertensives, tricyclics, MAO inhibitors, and dopamine agonists).
²