Sometimes it is not visible and the diagnosis is done by actually hearing the slap. Treated systematically, possible lesion sites causing foot drop include (going from peripheral to central):

Neuromuscular disease;
Peroneal nerve (common, i.e., frequent) —chemical, mechanical, disease;
Sciatic nerve—direct trauma, iatrogenic;
Lumbosacral plexus;
L5 nerve root (common, especially in association with pain in back radiating down leg);
Cauda equina syndrome, which is caused by impingement of the nerve roots within the spinal canal distal to the end of the spinal cord;
Spinal cord (rarely causes isolated foot drop) —poliomyelitis, tumor;
Brain (uncommon, but often overlooked) —stroke, TIA, tumor;
Genetic (as in Charcot-Marie-Tooth Disease and hereditary neuropathy with liability to pressure palsies);
Nonorganic causes, e.g. as part of a functional neurological symptom disorder.If the L5 nerve root is involved, the most common cause is a herniated disc. Other causes of foot drop are diabetes (due to generalized peripheral neuropathy), trauma, motor neuron disease (MND), adverse reaction to a drug or alcohol, and multiple sclerosis. Gait cycle
Drop foot and foot drop are interchangeable terms that describe an abnormal neuromuscular disorder that affects the patients ability to raise their foot at the ankle. Drop foot is further characterized by an inability to point the toes toward the body (dorsiflexion) or move the foot at the ankle inward or outward. Therefore, the normal gait cycle is affected by the drop foot syndrome. The normal gait cycle is as follows:

Swing phase (SW): The period of time when the foot is not in contact with the ground.
Keratosis pilaris atrophicans faciei  begins in infancy as follicular papules with perifollicular erythema. : 762   Initially, the lesions are restricted to the lateral eyebrows, but with time spread to involve the cheeks and forehead, and may also be associated with keratosis pilaris on the extremities and buttocks. : 762 : 714

See also
Skin lesion
Cicatricial alopecia
Ulerythema
List of cutaneous conditions

References


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