2. Figure 4.9 is a helpful diagram, repeated here in a clinical context: think of the level within the brainstem and of the dorso‐ventral plane. The usual hallmark is coexistence of damage to motor and/or sensory fibres and to cranial nerve nuclei. Syndromes involving oculomotor nerves III, IV and VI indicate upper or mid brainstem disease. Mid and lower brainstem disease affects nuclei VII–XII.
Bulbar and pseudobulbar palsy describe common brainstem syndromes (Chapter 13). Both cause dysarthria, dysphagia, drooling and respiratory problems. Bulbar palsy means disease of the lower cranial nerves (IX, X, XII), their nuclei and muscles. Pseudobulbar palsy is shorthand for UMN lesions of lower cranial nerve nuclei. MS, brainstem stroke and MND cause pseudobulbar palsy, the latter usually both pseudobulbar and bulbar. Advanced Parkinson’s causes poverty of movement of these muscles.
Figure 4.9 Brainstem: lateral schematic view.
Source: Hopkins (1993).
Anterior Horn Cell Disease
Relatively few diseases afflict the anterior horn. All are serious. The commonest is MND; spinal muscular atrophies, Kennedy’s disease, poliomyelitis and other viruses, notably West Nile are also causes. LMN signs of wasting and weakness develop. Amyotrophy is also a word used to describe wasting; it means myo (muscle) atrophy. Typically in all these diseases, initially at least, weakness can be highly selective. For instance, MND can present with weakness of one or two finger extensors. Neurophysiology is often diagnostic.
Sensory Abnormalities: Patterns at Different Levels
Sensation is difficult to evaluate. Eponyms abound – positive Tinel (carpal tunnel), tic douloureux, causalgia, anaesthesia dolorosa, lightning pains, Lhermitte, Brown‐Séquard, dissociated sensory loss, suspended sensory loss, sacral sparing, thalamic pain and astereognosis.
An approach that some find valuable is that if a sensory symptom is the principal complaint, such as the pain of trigeminal neuralgia (Chapter 13) or nocturnal tingling of the hands in median nerve entrapment at the wrist (Chapter 10), the quality of symptoms tend to be diagnostic. In other situations, the history and neurological signs suggest the diagnosis. The sensory signs that point to the level in a spastic paraparesis with cord compression are an example.
Figure 4.10 summarises principal patterns of sensory loss.
Peripheral Nerve Lesions
A lesion of an individual nerve produces symptoms and signs within its distribution. Demarcation is clear‐cut. Areas of sensory loss are discussed in Chapter 10. The quality of sensory disturbance varies between numbness, tingling and painful pins and needles. Painful tingling in the distribution of a damaged nerve when it is percussed, is known as a positive Tinel’s sign, for example in some carpal tunnel cases.
Neuralgia (Chapter 23) describes severe pain in the distribution of a nerve or root. In trigeminal neuralgia (tic douloureux; Chapter 13), the paroxysmal nature of pain, and its distribution are diagnostic.
Causalgia (Complex Regional Pain Syndrome, Chapter 23) describes chronic pain after nerve section or crush injury, sometimes following amputation. Anaesthesia dolorosa is pain in an anaesthetic area.
Polyneuropathy
Symmetrical, four limb, distal tingling, numbness or deadness are typical of polyneuropathy (Chapter 10).
Figure 4.10 Principal patterns of sensory loss.
Sensory Root and Root Entry Zone
Spinal and Vth nerve dermatomes are shown in Figure 4.11. There is sometimes overlap between adjacent dermatomes. Root pain is typically perceived both within the dermatome and within the myotome but tends to be less demarcated than pain with a single nerve lesion. For example, with an S1 root lesion from a lumbosacral disc, the sensory disturbance is down the back of the leg, without clear dermatome demarcation. Stretching the root by straight leg raising typically makes matters worse.
When a root entry zone is affected, within the cord, such as in tabes dorsalis, intense stabbing pains involve one or more spots, typically on the ankle, calf, thigh or abdomen – the lightning pains of tabes, seldom seen today.
Neuralgia, persistent burning root pain can follow shingles (post‐herpetic neuralgia, Chapter 23).
Figure 4.11 Spinal and V nerve dermatomes.
Cord Lesions: Sensory Changes
Posterior Columns
Patients describe:
Band‐like sensations, around trunk or limbs
Limb clumsiness, deadness
Numbness and burning
Electric shock‐like sensations.
Joint position sense, vibration, light touch and two‐point discrimination become diminished below the lesion. Stamping gait and pseudochorea of the outstretched hands are products of failing position sense.
Lhermitte’s sign is a sudden electrical sensation down the back, into the limbs produced by bending the head forward. Lhermitte’s suggests posterior column damage or occasionally caudal medulla. Lhermitte’s is seen in:
MS, typically in exacerbations
Cervical myelopathy, radiation myelopathy, trauma
Subacute combined degeneration of the cord
Occasionally:
