Clinical Presentation of Focal Nerve Lesions

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Neurosurgical Department, Friederiken-Hospital, Hannover, Germany

4.1 Diagnosis, Assessment, and Completion

Each focal neuropathy first needs a careful exploration of the patient’s history and evaluation of his clinical symptoms. Technical investigations remain as an additional option, though being of increasing importance, as mentioned previously. This statement is necessary insofar as today’s students and young physicians in neurologic departments tend to overrate modern imaging techniques as the primary diagnostic tool in every case. This holds true with regard to central nervous diseases as much as peripheral nerve lesions.

A list of questions to be asked in any case. First, there is a need to explore the patient’s history in detail: the kind and time of onset of symptoms, sudden or gradual onset, with or without a recallable incident, with or without previous inflammatory disease, progress and velocity of progress, which symptom occurred at first, which came in later, which increased; also questions about pain, time of onset, eventual disappearance and sudden motor deficits, quality, intensity, and radiation of pain, as well as dependence on extremity or hand-movement should be included; in this context, questions about habitual positioning of extremities during day or night may be useful in the search for information on pressure mechanisms.

Clinical examination. It should not be too time consuming to find the involved sensory area of the extremity: is it a dermatoma, autonomous nerve distribution field, or something in between – a question that allows one to distinguish between more centrally or more peripherally located lesions; the investigation of numb areas always needs to be compared with the contralateral extremity.

Next, a question about motor deficits will arise – are they referable to a root, nerve trunk, or a nerve branch; in the latter case an exact knowledge of its function and the site of its branch-off from the main trunk is required. Findings, in which a restriction of motor deficits on one single nerve distribution is lacking, are of special interest. This would indicate a lesion at a higher level or, quite another problem, an immunological-inflammatory disease. All the described differential-diagnostic disorders will then be discussed in Chaps. 5, 6, and 10.

Therefore, the existence of degenerative peripheral nerve diseases in a patient’s previous history is never to be neglected because it can simulate, conceal, or overlap a compression neuropathy, and it will also negatively influence the prognosis of nerve recovery.

Further clinical examination has to aim at a clear designation of which nerve is actually involved. Palpation and percussion of the presumably affected nerve trunk will help us: at different points of the suspected nerve, percussion will frequently trigger a typical electric current-like pain that the patient experiences in the sensory area associated with the nerve’s distribution field. The point where this triggered pain reaches a maximum can lead us to the location of the focal nerve involvement. Our opinion of this TINEL sign is that several nerve axons, after interruption of continuity, develop this irritability at their ends when re-sprouting begins. This represents a slight phantom pain elicited by axons in discontinuity. Its existence does not indicate the quantity of affected nerve fibers or the prognosis; but it does indicate axon involvement and its location.

Because of their outstanding importance, particularly concerning focal neuropathies including their assessment and therapy, we are going to dedicate associated pain types to the next chapter. In Chaps. 5 and 6, the large field of technical tools in diagnostics will follow – including neurography, electro-myography, and nerve ultra-sound sonography –which is essential as an additional guide towards a final diagnosis.

4.2 Pain Related Focal Neuropathies

Focal neuropathies associated with more or less severe pain need additional questioning in order to estimate the pain quality. When dealing with patients who suffer from nerve-related pain over months or even years, the physician will recognize their difficulties in describing their pain in their own words. Usually they start with how irritated they feel, how many daily activities are disturbed, how unbearable it feels to touch the painful skin area, or how pain-inducing a change of temperature is. Several patients say that they can demonstrate an especially hypo- or hypersensitive tissue area which they then suppose to be connected with the source of their pain. It is therefore of great importance to put carefully directed questions to make a correct pain assessment.

Entrapment syndromes of limb nerves generate a more or less bearable pain. It remains unexplained that the pain often does not remain restricted to the autonomous distribution area of the affected nerve; rather it appears diffuse and it usually disappears after nerve decompression. The carpal tunnel syndrome could be the best example, widely known, and associated with diffuse pain and immediate pain disappearance after surgical relief. This type of nerve trunk-related pain does not fit in with our nerve lesion classifications of the preceding chapter on the one hand, but also not with the concept of so-called nociceptive generated pain on the other. We only know that an intraneural and substantial nerve lesion predominantly does not exist in these cases. In addition, as mentioned before, we have no reliable knowledge about the substances or the structures which generate this type of pain. We only know that surgery has to be as gentle as possible to guarantee avoiding any substantial damage. If possible, the surgeon has to preserve paraneural and intraneural sliding capacities.

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