Anesthesia

Contents

  1. Definition and Clinical Terms
  2. Patterns of Anesthesia
  3. Anesthesia Dolorosa
  4. Treatment and Management

Definition and Clinical Terms

Anesthesia (or anaesthesia) is a complete loss of sensation, whereas hypoesthesia (hypoaesthesia, hypesthesia) refers to a diminution or reduction of sensation. In Jacksonian terms, these are considered "negative" sensory phenomena because they represent a loss of normal function.

Neurologically, localized anesthesia is most often encountered after the complete resection or lysis of a peripheral nerve segment. This is in contrast to paresthesia or dysesthesia ("positive" sensory phenomena), which typically reflect damage to a nerve that is still in continuity and in contact with its cell body.

Glove-and-stocking pattern of sensory loss

"Glove-and-stocking" anesthesia is a classic regional pattern of sensory loss seen in length-dependent peripheral neuropathies.

Patterns of Anesthesia

Anesthesia may involve all sensory modalities (global anesthesia, as induced in general surgical anesthesia) or be selective to specific pathways (e.g., thermoanesthesia for temperature, or analgesia for pain). In clinical neurology, specific regional patterns of anesthesia provide crucial localizing value:

  • "Glove-and-stocking" anesthesia: A distal, symmetric loss of sensation typical of length-dependent peripheral neuropathies.
  • "Saddle" anesthesia: A loss of sensation involving the S3-S5 dermatomes (the perineum, buttocks, and inner thighs), which is a hallmark warning sign of a cauda equina syndrome.

Anesthesia Dolorosa

Anesthesia dolorosa, or "painful anesthesia," is a paradoxical and distressing condition characterized by persistent, unpleasant pain (a positive sensory phenomenon) experienced in an area that is completely numb to external stimuli. It occurs in the distribution of a resected or deafferented nerve, for example, following neurolytic treatments for trigeminal neuralgia. The pain typically emerges with a delayed onset after the initial nerve injury or surgery.

Treatment and Management

While primary sensory loss (anesthesia) is generally managed by treating the underlying cause and preventing secondary injuries (like burns or ulcers in numb areas), the deafferentation pain of anesthesia dolorosa requires specific pharmacological intervention. This pain may respond to various neuromodulating medications, including:

  • Tricyclic antidepressants
  • Anticonvulsants (such as carbamazepine, gabapentin, and pregabalin)
  • Selective serotonin reuptake inhibitors (SSRIs)

 

Cross References

Analgesia; Dysesthesia; Neuropathy; Paresthesia